The countries featured in this volume have well-developed and effective systems for recruiting, preparing, developing, and retaining teachers and school leaders. Comparisons between countries are valuable for a number of reasons. First, they broaden the view of what is possible. Too often, policymakers remain stuck with conventional ideas, bound by precedents in their own context, and are unable to see options that might be available and successful. By providing policymakers with an expanded view of the policy choices that might be available, comparisons can expand the toolbox. Second, international comparisons show how ideas work in practice at the system level. By exploring other systems in depth, policymakers can see what the implementation challenges are, how other nations dealt with them, and what remains to be solved. Such explorations can help enable policymakers put in place new policies with a clearer eye.