Socioeconomic disadvantage is associated with lower early language/literacy (e.g., vocabulary, phonological processing, print knowledge), early math (e.g., numeracy), and self-regulation in young children prior to school entry (Clements and Sarama, 2011; Merz et al., 2014; Sabol and Pianta, 2017; Vrantsidis et al., 2020). In the self-regulation domain, socioeconomic disadvantage has been repeatedly associated with lower executive function in children (Lawson et al., 2018). These socioeconomic disparities in school readiness have been found to emerge early in life (Fernald et al., 2013; Noble et al., 2015) and are attributable to socioeconomic differences in children's early experiences (Bradley and Corwyn, 2002; Conger and Donnellan, 2007). For example, socioeconomic disadvantage often leads to reduced cognitive stimulation and increased chronic stress (e.g., household instability, noise/crowding, family conflict), which interfere with the development of school readiness skills in children (Gershoff et al., 2007; Pace et al., 2017). Socioeconomic disparities in school readiness likely partially explain the well-documented socioeconomic status (SES) opportunity gap that persists, or even widens, over time (Reardon, 2011). Children of minoritized racial and ethnic backgrounds (e.g., Black/African American, Hispanic/Latine) are disproportionately exposed to socioeconomic disadvantage in the United States (U.S.), often experience racial/ethnic discrimination, and have been found to exhibit lower school readiness (Palermo et al., 2018; Bustamante and Hindman, 2020).

Head Start is a comprehensive federally-funded ECE program in the U.S. that aims to increase school readiness skills in 3- and 4-year-old children from socioeconomically under-resourced families. Children from low-income families are eligible for Head Start. Head Start serves a range of racial/ethnic backgrounds, with most children reported to be Black/African American or Hispanic/Latine. Research spanning across decades has indicated that Head Start is only moderately effective at improving children's school readiness skills (Duncan and Magnuson, 2013; Jenkins et al., 2018; Duncan et al., 2023). Although significant impacts in the short-term have been documented, there is evidence that these effects are not maintained over time (Puma et al., 2012; Burchinal et al., 2024). Other studies have suggested that effects vary depending on multiple factors, including sample characteristics, initial skill level, and comparison group (Puma et al., 2010; McCoy et al., 2016).

Researchers have collaborated with Head Start programs to implement and test the effects of interventions designed to bolster school readiness in children. One promising approach consists of content-specific curricula (or curricular supplements) combined with professional development and coaching for teachers (Markowitz et al., 2018; Weiland et al., 2018). Content-focused (i.e., content-specific, skill-based) curricula target explicit skill growth by focusing on content areas following a developmental sequence and providing teachers with learning activities targeting specific skills (Jenkins et al., 2018; Joo et al., 2020). Coupled with intensive professional development, content-focused curricula have been found to improve school readiness among children in Head Start (Lonigan et al., 2011; Bierman et al., 2014; Morris et al., 2014; Schmitt et al., 2015; Jenkins et al., 2018; Nguyen et al., 2018; Weiland et al., 2018; Joo et al., 2020). Content-specific curricula have been found to improve children's outcomes in the targeted domain. For example, curricula targeting early math skills demonstrate efficacy in improving preschoolers' math concepts and skills (Clements and Sarama, 2007, 2008, 2011; Wakabayashi et al., 2020; Starkey et al., 2022).

Content-focused interventions targeting specific school readiness skills are inconsistent in improving other school readiness skills not targeted by the intervention (Sarama et al., 2012; Weiland and Yoshikawa, 2013; Morris et al., 2014; Schmitt et al., 2015; Upshur et al., 2019). Therefore, interventions have been designed that target more than one school readiness domain (Diamond et al., 2007; Barnett et al., 2008; Bierman et al., 2014; Farran and Wilson, 2014; Clements et al., 2020). For example, the combination of literacy- and math-focused curricula has been found to improve emergent literacy and math in children in a mixed set of preschool programs including Head Start programs (Lonigan et al., 2015). In addition, the Head Start REDI (Research-Based Developmentally Informed) program, which provides a supplemental curriculum targeting early language/literacy, socioemotional skills, and self-regulation along with professional development to teachers, demonstrates significant effects on language/literacy and self-regulation (Bierman et al., 2014; Welsh et al., 2020).

However, few studies have examined skill-based curricula focused simultaneously on early language/literacy, math, and self-regulation. In one study, positive effects were found in all three school readiness domains (Lonigan et al., 2015). In another prior study, an intervention in which teachers implemented circle time self-regulation games with embedded math and literacy content was found to have positive effects on early math and self-regulation but not early literacy (McClelland et al., 2019). In the current study, we add to this literature by examining the effects of an early intervention targeting early language/literacy, math, and self-regulation by enhancing the classroom and home environments on children's school readiness.

Another intervention approach is to focus on the family context to improve school readiness in children in Head Start. Parents' warm, responsive, and stimulating interactions with children have been found to support early socioemotional and cognitive development (Merz et al., 2015). In addition, parental involvement in children's early learning and education supports development in multiple domains (Barger et al., 2019; Jeon et al., 2020; Cosso et al., 2022). In socioeconomically under-resourced families, on average, less time is spent on children's learning activities (e.g., book reading), fewer learning materials and experiences are provided, and there are fewer or lower-quality adult-child conversational exchanges compared to more resourced families (Bradley and Corwyn, 2002; Conger and Donnellan, 2007; Gershoff et al., 2007; Guryan et al., 2008; Pace et al., 2017).

A range of parent- and home-based interventions have been designed as “add-ons” to Head Start programming. Many have been found to improve parenting knowledge, quality of parent-child interactions, parent engagement in children's learning, and children's school readiness skills (Welsh et al., 2014; Joo et al., 2020; Bierman et al., 2023). For example, interventions that work with parents to support their use of learning activities at home and emphasize family-school partnership lead to increased school readiness in children (Sheridan et al., 2010, 2011; Welsh et al., 2014; Bierman et al., 2015; Magnuson and Schindler, 2016; Joo et al., 2020).

Classroom-based interventions supplementing Head Start programs have often overlooked the important role that parents play. This decision ignores the importance of continuity in learning experiences between school and home and the key role of parental engagement in children's education (Welsh et al., 2014; Jones et al., 2017). Although home- and preschool-based interventions significantly increase support for school readiness in the home and classroom, respectively, children may not experience support across these contexts. Only a few studies have examined the effects of early interventions that target both the classroom and home environments on children's school readiness skills (Anthony et al., 2014; Landry et al., 2017, 2021; Young et al., 2023). For example, the Head Start REDI parent (REDI-P) program with aligned home and classroom components has been found to improve language/literacy and socioemotional skills in children (Bierman et al., 2015). Taken together, there is a gap in research examining the benefits of supplemental, skill-based curricula targeting early language/literacy, math, and self-regulation through integrated classroom and home components. The present study aimed to fill this gap.

The GRS intervention provided a supplemental curriculum targeting the development of language/literacy, early math, and self-regulation by enhancing the classroom and home environments (Noble et al., 2012). The intervention was designed to increase teachers' and parents' use of simple, sequenced learning activities intended to foster the development of school readiness skills in children (Marti et al., 2018a). Given the co-development of pre-academic and self-regulatory skills during early childhood, GRS learning activities were designed to simultaneously support the development of these skills through a single, content-focused curriculum aligned across the classroom and home contexts (Marti et al., 2018b) (see Supplementary material). Prior work involving a pilot cohort and the first and second cohorts of children who participated in the current study showed that the GRS intervention was implemented by teachers, on average, with moderate-to-high fidelity and that most teachers followed the recommended dosage (Noble et al., 2012; Marti et al., 2018a). In addition, 68% of parents attended at least one GRS parent event, and 81% reported spending at least 10–30 min a week doing GRS activities with their children (Marti et al., 2018b).

Many of the children Head Start serves are Hispanic/Latine, and current estimates indicate that the number of Hispanic/Latine children in Head Start is rapidly increasing (Vespa et al., 2018; U.S. Department of Health Human Services, 2022). Although not a homogeneous group, Hispanic/Latine children have a unique set of strengths and needs that are important to consider. For example, they are more likely to be dual language learners (DLLs), as Spanish is often spoken in the home. Although Hispanic/Latine children are found to exhibit lower pre-academic skills prior to school entry, research suggests that approaches to learning and executive function may be strengths that Hispanic/Latine bilingual children bring to the classroom (Carlson and Meltzoff, 2008; Galindo and Fuller, 2010; Choi et al., 2018; Bustamante and Hindman, 2020). For these reasons, studies of early interventions should take into account the needs of this population. The GRS intervention was designed to be accessible and responsive to the cultural backgrounds and experiences of Spanish-speaking families.

The goal of this study was to examine the effects of the GRS intervention on school readiness skills in children in Head Start programs. Participants were 3- and 4-year-olds who were primarily Hispanic/Latine and from Spanish-speaking homes. Specifically, we examined whether children in the intervention group showed greater gains from pretest to posttest in language/literacy (vocabulary, print knowledge, phonological awareness), early math, and self-regulation (e.g., executive function) compared with children in the Head-Start-as-usual comparison group. We hypothesized that children in the intervention group would demonstrate greater gains in these school readiness skills compared to children in the comparison group.

Seven Head Start centers in a large Northeastern city in the U.S. were recruited across three cohorts (2014–2015, 2015–2016, 2016–2017 academic years). Thirty-eight classrooms in these centers participated in the study. Across these 38 classrooms, 31 teachers participated in the study; six teachers participated in the study in the same group (intervention or comparison) in more than one cohort. One classroom was excluded from analyses, as the lead teacher was removed from her position mid-year, resulting in the analysis of 37 classrooms and 30 teachers. Of the families with children in these classrooms, 86% consented to participate; 14% did not have parent/guardian consent to participate in the study.

Twenty classrooms were assigned to receive the intervention, and 17 were assigned to the Head Start-as-usual comparison group. These assignments were non-random as several Head Start directors chose which teachers would participate in which condition. Six centers used the Creative Curriculum (Dodge et al., 2002) and one used the HighScope curriculum (Michael-Luna and Heimer, 2012); both are whole-child (global) curricula. All study procedures were approved by the Columbia University Medical Center Institutional Review Board. Parents or guardians provided written informed consent for children to participate in this study.

At pretest (start of the fall semester) and posttest (end of the spring semester), GRS staff administered school readiness tasks to children. There was an average of 7 months between pretest and posttest, and time between pretest and posttest was considered for inclusion as a covariate in analyses. At each timepoint, children completed two 20- to 30-min testing sessions on different days. Tasks were administered to children by bilingual assessors in a fixed order. Additionally, parents completed demographic questionnaires, which included items on maternal education, family income, child race and ethnicity, and language spoken in the home.

All analyses were conducted in SAS (version 9.4) (SAS Institute, Cary, NC). Multilevel modeling was used to examine whether the GRS intervention improved children's school readiness skills. Children were nested within classrooms (M = 14 children per classroom, SD = 3.67) within Head Start centers (N = 7). Most outcome variables exhibited variability at the classroom level, with intraclass correlations (ICCs) ranging from 0.00 to 0.16 (p = 0.002–0.19; see Supplementary Table S1). Head Start center-level variances of posttest outcome measures ranged from 0.00–0.11 (p = 0.07–0.18). In total, repeated observations (level 1) were nested within children (level 2) who were nested within classrooms (level 3) within Head Start centers (level 4). Initial analyses including Head Start center (dummy-coded; N = 7) as a covariate indicated nonsignificant effects; thus, Head Start center was not included in the final models. Therefore, multilevel models specifying random child- and classroom-level intercepts were conducted to account for nesting within children and classrooms (Raudenbush and Bryk, 2002). These analyses were conducted using the mixed procedure and restricted maximum likelihood estimation with Kenward-Roger degrees of freedom. Using this analytic approach, children with complete data for the predictor variables were included in analyses even if they had missing data for the outcome variable.

Children's school readiness outcomes (eight total) were modeled as a function of group (intervention, comparison), time (pretest, posttest), and the group-by-time interaction. Separate models were run for each outcome (three early language/literacy, two early math, and three self-regulatory skills). Age, sex, race/ethnicity, and cohort were included as covariates. The group-by-time interaction is key to understanding whether change over time differed for the intervention group compared to the comparison group (or whether the effect of the intervention was different at pretest compared to posttest). Although we initially included time between pretest and posttest and pretest classroom quality as covariates, they did not significantly contribute to the final estimates and were removed from the models for parsimony. False discovery rate (FDR) corrections (Benjamini and Hochberg, 1995) were used to control for multiple comparisons within each school readiness domain (DiPerna et al., 2018; U.S. Department of Education, 2021).

Effect size (ES) for intervention effects was calculated as a Cohen's d type statistic, based on the difference between posttest means that were adjusted for pretest (and other child- and classroom-level covariates), then divided by the pooled pretest group standard deviations (Bierman et al., 2015; Landry et al., 2017, 2019; DiPerna et al., 2018). Cohen's d statistics around 0.20, 0.50, and 0.80 represent small, medium, and large effects, respectively (Cohen, 1992).

The intervention and comparison groups did not differ significantly at pretest in vocabulary (p = 0.31), print knowledge (p = 0.20), phonological awareness (p = 0.09), quantitative reasoning (p = 0.55), early math skills (p = 0.51), executive function (p = 0.06), inhibitory control (p = 0.34), or attention/impulse control (p = 0.15).

The group-by-time interaction was significant for vocabulary, as measured by the EOWPVT, and print knowledge, as measured by the WJ Letter-Word Identification subtest (see Table 4). Vocabulary and print knowledge significantly increased over time in both groups but increased more steeply among children in the intervention group (see Figure 1). At posttest, compared to children in the comparison group, children in the intervention group had significantly higher vocabulary, t(27.4) = 2.48, p = 0.02, ES = 0.34, but not print knowledge, t(33.4) = 0.39, p = 0.70, ES = 0.03. Adjusted means across groups are presented in Table 4. There were no significant effects for phonological awareness. Full results of the final models are provided in Supplementary Table S3.

The group-by-time interaction was significant for quantitative reasoning, as measured by the WJ Applied Problems subtest, and early math skills, as measured by the REMA-SF (see Table 4). Quantitative reasoning and early math skills significantly increased over time in both groups but increased more steeply among children in the intervention group (see Figure 2). The groups did not differ significantly in quantitative reasoning, t(39.5) = 0.93, p = 0.36, ES = 0.12, or early math skills, t(36.2) = 1.20, p = 0.24, ES = 0.19, at posttest. Full results of the final models are provided in Supplementary Table S4.

There were no significant group-by-time interactions for scores on the HTKS or toy wrap tasks or assessor-reported attention/impulse control (see Table 4). Full results of the final models are provided in Supplementary Table S5.

The group-by-time interactions for vocabulary, print knowledge, quantitative reasoning, and early math remained significant after additionally controlling for pretest and posttest assessment language. In addition, there were no significant interactions between group and cohort or between group and classroom age (all 4-year-olds versus mixed 3- and 4-year-olds).

In the language and literacy domain, compared to children in the comparison group, children in the intervention group made greater gains over time in vocabulary and print knowledge but not phonological awareness. At posttest, the intervention group had significantly higher vocabulary skills than the comparison group, with a small-to-medium effect size. Group differences in print knowledge and phonological awareness at posttest were not significant. In addition, the intervention group made significantly greater gains over time in early math compared to the comparison group. Although not statistically significant, the intervention group scored higher in early math at posttest than the comparison group, with a small effect size. It is recommended that effect sizes be considered in conjunction with statistical significance (Wasserstein and Lazar, 2016). Thus, results were strongest for vocabulary but encouraging for early literacy and math skills, as the intervention group exhibited greater gains over time in these skills compared to the comparison group.

Results for vocabulary, and to a lesser extent early literacy and math, are consistent with previous work. For example, skill-based curricula targeting early language/literacy have been found to improve oral language in children in Head Start programs (Jenkins et al., 2018; Joo et al., 2020). Increases in vocabulary may lead to increases in other school readiness skills, as oral language development can be a precursor to developmental advances in other domains (Purpura et al., 2011).

It is not possible to pinpoint what may be driving this intervention effect. One possibility is that the structure and content of GRS activities may have encouraged teachers and parents to engage in more enriching conversations and use new vocabulary, which improved children's vocabulary skills. In addition, the individualized weekly coaching teachers received may have been a key feature of the intervention. Another contributing factor may have been the linguistic and cultural responsiveness of the intervention, as all GRS materials were designed to be culturally sensitive, were pilot tested in bilingual classrooms, and home activities and videos for parents were translated into Spanish (Marti et al., 2018a,b). Our methods, though, do not allow insights into the extent to which the classroom or parent component of the intervention was responsible for improvements in language and early math.

The overall pattern of results for pre-academic skills suggests that the GRS intervention could have positive impacts on early language/literacy and math, two core school readiness domains. There was a pattern of increases over time in pre-academic skills favoring the intervention group. Although some content-specific interventions targeting early math or literacy/language skills have demonstrated spillover effects on other pre-academic skills that were not targeted by the intervention, these effects have not been consistently observed (Sarama et al., 2012). The current results are consistent with the idea that content-specific interventions targeting both early language/literacy and math may improve both early language/literacy and math but prompt further discussion about possible adjustments to the intervention that could make it more effective.

Although the results for pre-academic skills are encouraging, the GRS intervention did not significantly improve children's self-regulatory skills. Thus, taken together, it is important to consider why the intervention was not more effective. One possibility is that increased teacher and parent use of the GRS activities may have led to greater improvements in school readiness skills in children. Although teachers implemented the intervention with moderate-to-high fidelity (dosage, adherence fidelity) on average, there was variability in intervention fidelity across classrooms (Marti et al., 2018a). Higher intervention fidelity in the classroom was associated with greater gains in early literacy, math, and self-regulation among children (Marti et al., 2018a). Some teachers may have needed more intensive professional development and coaching to implement the intervention with higher fidelity. Similarly, prior results indicated variability in parental involvement in the GRS intervention (Marti et al., 2018b). Greater parental involvement in the intervention was significantly associated with greater gains in children's early literacy, math, and self-regulatory skills (Marti et al., 2018b). Thus, greater parental engagement, and more support for parental use of GRS activities at home, may have led to greater gains in school readiness skills. Many early interventions have reported facing challenges with parental engagement, as low access to socioeconomic resources and other factors make it difficult for parents to enroll and participate in parent programs and interventions (Gennetian et al., 2019). Future studies should focus on effective strategies to increase parental engagement (Bierman et al., 2023).

Another possibility is that providing activities targeting all three school readiness domains may have been demanding for teachers in terms of instructional time and organization, and this may have reduced the intensity and frequency of certain GRS activities. Although evidence suggests that teachers' completion rates did not vary across language/literacy, early math, and self-regulation activities (Marti et al., 2018a), teachers may have spent less time on self-regulation activities than early literacy and math activities, yielding lower impacts. However, our intervention fidelity measures did not allow us to test this possibility, as we did not measure time spent on activities in each school readiness domain. In addition, our intervention fidelity measures did not capture the repetition of activities.

Finally, some interventions found to improve children's self-regulation have focused on improving classroom management as a means of improving self-regulation. For example, some interventions that emphasized providing teachers with professional development and coaching on classroom management have significantly improved children's self-regulation (Raver et al., 2011; Morris et al., 2013). Thus, further integrating enhanced teacher professional development to improve classroom organization and management into the GRS intervention may lead to significant gains in children's self-regulation (Lonigan et al., 2015). This approach may be especially effective if paired with a parenting-focused component (Bierman et al., 2023). Future research should use a randomized controlled design to examine whether a modified version of the GRS intervention leads to more pervasive increases in school readiness skills with larger effect sizes.

Most children in this study were Hispanic/Latine DLLs. Many children who are DLLs exhibit significant delays in their language and early literacy skills in preschool. Research suggests that teachers need specific support and instructional strategies to address early literacy skills in this population (Zepeda et al., 2011; Jacoby and Lesaux, 2017). The GRS intervention did not provide teacher training on specific strategies to meet the learning needs of DLLs. Research is beginning to identify specific intervention approaches with teacher professional development components that bolster early literacy skills in DLLs (Buysse et al., 2010; Larson et al., 2020). For example, early interventions that emphasize small-group, bilingual language and early literacy instruction have been found to increase language and literacy skills in DLLs (Méndez et al., 2015; Landry et al., 2019). Although a strength of the GRS intervention is its linguistic and cultural responsiveness, future versions of the intervention should further adapt the classroom component to Hispanic/Latine DLLs, who are increasingly served by Head Start programs.

This study had a number of strengths. GRS is an evidence-informed early intervention that involved a skill-based supplemental curriculum, support for learning in the home environment, and professional development and coaching for teachers. Most of the children who participated in this longitudinal study were Hispanic/Latine, one of the fastest growing populations in the U.S. (Vespa et al., 2018), increasingly served by Head Start (U.S. Department of Health Human Services, 2022) and understudied. Strengths of this study also included the use of direct assessments of multiple school readiness skills and use of the PreLAS as a routing measure to determine language dominance in DLLs. This study also had a high retention rate from pretest to posttest and a rigorous analytic approach.

This study also had limitations that should be considered when interpreting the findings. First, we employed a non-randomized, quasi-experimental design, limiting our ability to make causal inferences. There were no significant group differences in most classroom, teacher, and family characteristics, or pretest school readiness skills. However, comparison classrooms were rated higher in quality than intervention classrooms at pretest. Second, implemented self-regulation measures may not have captured all the specific components of self-regulation that the intervention targeted. Indeed, some previous intervention studies have demonstrated effects specific to certain executive function components or measures (Bierman et al., 2014). Psychometric issues with the self-regulation measures, such as floor effects with the HTKS task (Gonzales et al., 2021), may also have affected the results for self-regulation. Third, in 2016, universal pre-kindergarten was being rolled out, and most Head Start classrooms were participating in some capacity during the study. Although we accounted for potential classroom and cohort effects, pre-kindergarten was not implemented equally across centers. Thus, unmeasured variables such as teachers across the intervention and comparison classrooms implementing Department of Education recommended curricula or Units of Study may have presented a confounding factor of intervention effects. Fourth, to capture the full development of school readiness skills in DLLs, children need to be assessed in both languages (Peña and Halle, 2011; Méndez et al., 2019; Guzman-Orth et al., 2017). Therefore, testing DLLs in both languages may have led to more comprehensive insights into their school readiness skills. Fifth, some of the classroom observations were conducted by GRS staff who were certified CLASS observers.