Beginning in 2012, the Boston Public Schools (BPS) Department of Early Childhood rolled out a curricular and professional development approach called Focus on Early Learning that aimed to align content, instruction, and teachers’ training and coaching from Pre-K to 2nd grade. To experience full curricular alignment from Pre-K to kindergarten, students must attend both a BPS Pre-K and a BPS kindergarten implementing Focus on Early Learning. However, enrollment in a BPS Pre-K is optional and not all children attend a BPS Pre-K before entering kindergarten. Additionally, school adoption of Focus on Early Learning is optional. This means that BPS Pre-K non-attenders make up two groups – those who experienced aligned kindergarten and those who did not. In all, our sample includes a total of 290 BPS Pre-K non-attenders who attended kindergarten in BPS in the 2017-2018 school year. Out of the 290 non-attenders, 239 students in 40 different schools attended an aligned kindergarten program, and 51 students in 7 different schools attended an unaligned kindergarten program (Figure 1). We first compare the demographic characteristics of Pre-K non-attenders who experience aligned and unaligned kindergarten. We then answer the question: Do BPS Pre-K non-attenders make larger gains in their math, language, literacy, and executive function skills in an aligned or unaligned kindergarten program? (author abstract)