The design and effects of a data-based approach to training school staff in the implementation of innovative programs are discussed. The rationale and design of the Data-Based Staff Development Program, which has been developed to train school staff to implement the programmatic and personnel changes required to effectively establish and maintain an innovative program, the Adaptive Learning Environments Model (ALEM), in classroom settings, are outlined. This program is designed specifically to help school personnel improve their knowledge and skills in providing learning experiences that are adaptive to student differences, particularly in the context of the effective mainstreaming of exceptional students in regular classrooms. Findings from a study investigating the effectiveness of using the data-based approach to staff development in improving classroom implementation of the ALEM are discussed. Data from the study are reported as preliminary evidence of the effectiveness of the data-based approach to staff development, and future lines of work in this area are suggested. (Author/CJB)