Objective: The purpose of the current study was to examine the practice validity of a new ecological assessment instrument for third through fifth graders in terms of whether it provided school staff with new knowledge about students. Method: Preassessment knowledge of school staff was compared to data obtained from 21 children and their parents on 29 measures. Data were collected using the Elementary School Success Profile. School staff preassessment knowledge was compared to obtained data across seven domains of children's lives (neighborhood, school, family, peers, parent educational involvement, well-being, and home behavior), data sources (child and parent), and grade level of students. Results: Preassessment knowledge was not highly correlated with obtained data; preassessment expectations matched obtained data only about 41% of the time, and knowledge varied by domain, source, and grade level. Conclusions: Ecological assessments can address gaps in school staff's knowledge of targetable factors that influence the success of students. (Contains 3 tables.)