The report summarizes the first two phases of project IMPACT (Implementing Mainstreaming Programs through Active Cooperative Training), a Montgomery County, Pennsylvania approach using a committee format for analyzing and addressing mainstreaming needs. A needs assessment instrument examining four aspects of concern about mainstreaming was developed (curriculum considerations, school management issues, mainstreaming procedures, and inservice training), and data for four target schools and four control schools are compared. Results of the needs assessment and a mainstreaming survey are explained to indicate the positive effects of Project IMPACT in areas of procedures, curriculum, and management. Additional findings revealed that inservice programs appeared to have helped teachers become more comfortable with some aspects of mainstreaming. Extensive appended information includes case studies from both phases of the project of the target schools, with demographic data and discussion of committee decisions and activities; and tables of descriptive statistics of target schools' pre- and posttest performance on the mainstreaming needs assessment. (CL)