This paper evaluates the impact on student achievement made by eight New York City alternative high schools. The schools serve students with histories of poor attendance and low academic achievement, so an emphasis is placed, in the first section of this report, on findings which reveal students' credit accumulation and attendance patterns in their first semester. Comparisons are drawn between students' performances at their earlier schools and at the alternative schools, and among the different alternative schools themselves; improved student achievement at most of the alternative schools is reported. To verify this finding and to define the characteristics of successful alternatives, the report's second section provides case studies of three successful schools. A school-by-school profile is followed by a discussion of student and teacher satisfaction, school organization and programs, and effective school climates. Finally, general recommendations, addressed mainly to policy makers, are given. Appendices contain student population data from all eight alternative schools and research instruments. (KH)