This study examines the impact of preschool attendance on early academic achievement gaps using longitudinal data from a nationally representative sample of over 600 twin pairs. The research aims to determine whether preschool reduces inequalities in early academic achievement by providing disadvantaged children with higher-quality learning environments. Key findings include: 1. **Preschool Attendance and Shared Environmental Influences**: Attending preschool at age 4 was associated with reduced shared environmental influences on reading and math skills at age 5, but not on cognition at age 2. These effects were mediated by reductions in achievement gaps related to minority status, socioeconomic status, and parental stimulation. 2. **Socioeconomic Status and Preschool Enrollment**: Lower socioeconomic status was linked to lower rates of preschool enrollment, suggesting that the children who would benefit most from preschool are the least likely to attend. 3. **Longitudinal Analysis**: The study used structural equation models to estimate the contributions of genes, shared environment, and nonshared environment to cognition and achievement scores. The results indicate that preschool attendance significantly reduces the influence of family-level characteristics on achievement, particularly for racial and ethnic minorities, children from lower SES families, and those with less cognitively stimulating parents. 4. **Discussion**: The findings suggest that preschool may help reduce achievement gaps associated with family-level variables, but the equalizing effects may not fully materialize due to lower-socioeconomic status families being less likely to send their children to preschool. Future research should focus on the specific aspects of preschool quality and the long-term persistence of these effects. The study highlights the importance of early childhood education in addressing social inequalities in academic achievement and underscores the need for more equitable access to high-quality preschool programs.This study examines the impact of preschool attendance on early academic achievement gaps using longitudinal data from a nationally representative sample of over 600 twin pairs. The research aims to determine whether preschool reduces inequalities in early academic achievement by providing disadvantaged children with higher-quality learning environments. Key findings include: 1. **Preschool Attendance and Shared Environmental Influences**: Attending preschool at age 4 was associated with reduced shared environmental influences on reading and math skills at age 5, but not on cognition at age 2. These effects were mediated by reductions in achievement gaps related to minority status, socioeconomic status, and parental stimulation. 2. **Socioeconomic Status and Preschool Enrollment**: Lower socioeconomic status was linked to lower rates of preschool enrollment, suggesting that the children who would benefit most from preschool are the least likely to attend. 3. **Longitudinal Analysis**: The study used structural equation models to estimate the contributions of genes, shared environment, and nonshared environment to cognition and achievement scores. The results indicate that preschool attendance significantly reduces the influence of family-level characteristics on achievement, particularly for racial and ethnic minorities, children from lower SES families, and those with less cognitively stimulating parents. 4. **Discussion**: The findings suggest that preschool may help reduce achievement gaps associated with family-level variables, but the equalizing effects may not fully materialize due to lower-socioeconomic status families being less likely to send their children to preschool. Future research should focus on the specific aspects of preschool quality and the long-term persistence of these effects. The study highlights the importance of early childhood education in addressing social inequalities in academic achievement and underscores the need for more equitable access to high-quality preschool programs.