The two research projects described and discussed in the special issue provided much
needed longitudinal empirical data to show the curricular influence on classroom
instruction and student learning outcomes. The findings have helped to advance our
understanding of whether the reform curricula can bring about positive changes in
classroom instruction and student learning outcomes and how such changes might be
sustained. In this article we synthesize the results from the two studies and discuss several
lessons learned from the projects about investigating and understanding curricular effects
on the teaching and learning of mathematics.