Research Findings: The present study examined the amount of exposure to math activities that children of low socioeconomic status (SES) encounter in private community-based preschool classrooms and whether greater time in these activities predicted higher math skills. Three cohorts of 4- to 5-year-old children were recruited from 30 private centers, resulting in a sample of 288 children nested within 73 preschool classrooms. Classroom observations were conducted for 150 min during fall and winter of the preschool year using a time sampling method. Preschoolers were exposed to an average daily amount of 2 min (range = 0-23) of math exposure. Hierarchical linear models were run to examine associations between math exposure and math achievement. Children's exposure to math activities significantly and positively predicted their spring math scores, but associations between math exposure and math scores were stronger for children with lower initial cognitive abilities and self-regulation skills. Practice or Policy: Our findings revealed generally low levels of math instruction occurring in private child care centers primarily serving low-SES children. Even limited exposure to math activities predicted children's math skills, however, which highlights the importance of math content in these settings. (author abstract)