[영문]The Elementary School Success Profile (ESSP) is a social environmental assessment tool that collects data from third, fourth, and fifth graders, their parents or guardians, and their teachers. Ensuring the validity of the data collected with the child-report component was a primary concern during the development of the ESSP. This article describes how cognitive testing was used to promote the validity of ESSP child-report data. Four types of response problems were identified in data collected from 58 children. Strategies to address problems are described, and evidence of the association between item modifications and improved performance is presented. Cognitive testing is recommended as a standard procedure in the development of child-report instruments.