There is near universal consensus that high-quality early care and education can promote children's readiness for school and reduce income-based achievement gaps at school entry. Yet, the promise of preschool can only be realized when the field has a clear conceptualization of the most salient quality indicators that contribute to children's development. Past research in this area has primarily focused on the contribution of average classroom experiences in preschool settings on child outcomes. Characterizing children's average classroom experiences can inform broad, teacher-level interventions to increase classroom quality. However, it may miss the fact that individual children have different experiences than the average student which may serve as an important and malleable target for individualized school-based interventions. Surprisingly, there is little descriptive research on the extent to which children's engagement varies within classrooms or even within individual children from day-to-day. To address this gap, the current study utilizes three large-scale early childhood education datasets (NCEDL, SWEEP, and LAExCELS) to explore how children's engagement, measured by moment-to-moment time sampling, varies within classrooms and explores if variation in levels and quality of child engagement and activity type/setting is associated with children's outcomes.