Research Findings: Three former teaching colleagues at the University of California's Harold E. Jones Child Study Center discuss an interpretative approach to child observation and assessment and how this approach was developed (1970s-2005) within this lab school's early childhood education setting. With teaching practice shaped and driven by a tradition of teacher research, they reconceptualized the classroom "learning centers" as social ecologies and studied children's play, learning, and development using interaction as the unit of analysis. In this approach, teachers create spaces for inquiry, observe, interpret, reflect on understandings, document and evaluate settings for learning, and formulate next steps. They report on and refine social ecologies from the point of view of the children while adapting to the full-time child care and preschool needs of university families. Practice and Policy: The authors of this paper focus in particular on details of classroom research they themselves conducted from which the interpretive approach evolved, as well as on those figures who contributed to their thinking and whose work and writing informed those studies. (Contains 1 table and 3 figures.)