To identify critical postimplementation events and school-related factors that affect the continuation of new classroom practices, qualitative data were collected in 14 elementary and secondary schools representing a mix of settings. Efforts to improve the schools' instructional programs in either basic skills, career education, or citizen education had been aided with formal school improvement activities. After 12 to 24 months, researchers, in a followup study, assessed the practices of teachers and administrators to determine whether the new practices were still being used. The data suggest that the most important factor supporting teachers' continuation of the new practices was support from the building administrator, though in some grades or departments support from other teachers contributed to the continuation of practices. The revision of curriculum guides facilitated the continuation of practices and helped ease the adjustment of new teachers. Finally, assessment of effectiveness by teachers affected continuation of practices in two districts. Additional analysis examined school organizational factors that affected the likelihood of occurrence of these events. (MLF)