This fall, the Madison Education Partnership (MEP), in collaboration with the Madison Metropolitan School District’s Departments of Early Learning and Research & Innovation, began an evaluation of the first year of the District’s full-day 4K program. The District chose to initially offer full-day 4K programming at schools that serve relatively high numbers of students of color and students from families that are economically constrained as part of an equity strategy to address persistent gaps in outcomes by targeting those groups who historically have come in, on average, lower-performing. We recently completed our first round of data collection, assessing dimensions of children’s executive function and numeracy skill around the time they begin 4K. We found: In line with the design of the full-day 4K roll-out, full-day classrooms on average include more students of color and fewer children whose parents enrolled in college than do half-day classrooms; At the start of 4K, students in full-day sections score slightly lower on average than their half-day counterparts in early literacy, early numeracy, executive function, and social-emotional skills; These differences in baseline scores, however, are relatively small and do not undermine the evaluation design. (author abstract)