This is an integrated report on 28 ongoing projects that were set up to study and improve American high schools on a large scale. The activities include establishment of a national data base on high school students; a study of new standards for college admission; administrators' reports on what works in urban schools; intensive studies of single schools; and new proposals for a general education curriculum. The report (1) describes projects' central concerns, anticipated outcomes, and methodologies; (2) summarizes existing knowledge about secondary education and the extent to which the projects may enhance knowledge about high school students' characteristics, program offerings, teaching methods, institutional determinants of effective education, school-community relationships, and school improvement; and (3) identifies possibilities for school improvement through changes in program content, staff performance, school climate, school-community relationship, and institutional factors. The report furthermore points out significant issues that are not addressed by the different projects' approaches for reform. (Author/MJL)