The book is an account of the development of the credit system now in general use in Ontario high schools. The author describes education in the province from its inception, with particular emphasis on the reorganization begun in the middle 1960s. The text covers the background information, points up some of the trends of the last decade, and describes some of the forces and the people important to the implementation of change in the Ontario secondary education system. The effects in different schools of the implementation of innovations such as subject promotion, ungraded hours, subject choice available to students, and diplomas based on the number of credit hours achieved are described. Other proposals for change and an evaluation of one school that adopted some innovations are also presented. (Author/JF)