Initial efforts to validate a developmentally appropriate assessment system for use with children aged 3 to 7 years are described. The Project Construct Assessment System is part of a comprehensive framework for curriculum and assessment that is predicated on the theory that children construct their own knowledge. It features a variety of performance-based methods that can be used to monitor students' progress on 26 curricular goals. Extensive validation procedures, which include traditional methods as well as newer approaches proposed specifically for performance assessments, have been incorporated into the construction of the assessment system. Initially, 15 members of a statewide advisory group of educators evaluated the specifications for the instrument. Parts were pilot tested by over 100 teachers, and the proposed Goals for Students of the project were validated through a survey responded to by 647 early childhood teachers and school administrators in Missouri (represents a 38 percent response rate). The development of the Project Construct Assessment System demonstrates that consensus between measurement specialists and educators from other fields can be achieved through collaboration. One table presents information about the validation survey. Appendixes contain the Goals for Students and an example of a curriculum specification. (SLD)