The study examines the defining features of school improvement programs. Twelve research-based programs that have been implemented for 5 or more years in at least 50 schools or for 3,000 students were analyzed. All have achieved national visibility. Eight of the programs focused on curricular reform and topics included: (1) Core Knowledge; (2) Different Ways of Knowing; (3) Foxfire; (4) Higher Order Thinking Skills; (5) the National Writing Project; (6) Paideia; (7) Reading Recovery; and (8) Success for All. The other four programs (Accelerated Schools, the Coalition of Essential Schools, Community for Learning, and School Development) were comprehensive models focusing on improving student learning in all subject areas. The programs are distinctive, but share the intention to increase learning through research-based practices. Researchers identified 54 practices among the 12 programs, and considered 26 practices strongly research-based. The programs have a variety of pre-implementation preparations and implementation requirements, and they vary in the amount of time and costs required for implementation. There is a great deal of information about many aspects of these programs, but there is a relative lack of information about their effects on achievement. (Contains 3 tables and 15 references.) (SLD)