Students experience a variety of challenges as they move from one level in school to the next. In this session, we consider and discuss two central questions related to students' progressions through their mathematical experience, particularly at transitions roughly characterized as elementary to middle school, middle school to high school, and high school to post-secondary: What are the key dimensions/aspects of such transitions? What kinds of system-level responses address students' issues with transitions, particularly when they are problematic? We discuss research and practice related to students' challenges and the nature of system-level responses to various aspects of these school mathematics transitions, including mathematical content, curriculum, students' dispositions, classroom teaching practices, and school structures. Characteristics of selected strategies and programs are discussed and questions for further research are presented. [For the complete proceedings, see ED584829.]