This study extended existing work on the Individualized Classroom Assessment Scoring System (inCLASS), established as a measure of preschool-age children's observed interactions in the four domains of Teacher Interactions, Peer Interactions, Task Orientation, and Negative Engagement. Our sample included kindergarten-age children (N = 117; mean age = 5.53 years) in 11 classrooms in four schools from a low-income community. We had three aims: (a) examine the inCLASS' applicability in this new sample, (b) examine associations with teacher reports of children's social skills and learning behaviors, and (c) identify characteristics at the time point, child, and classroom levels that contribute to inCLASS scores. We found limited variability in scores for each of the four inCLASS domains, with scores related to teacher reports of children's skills as expected. Children's inCLASS scores were highly variable from one observation time point to the next, and time point, child, and classroom characteristics differentially contributed to their scores. Implications for observational assessment are discussed.