I can’t believe I’ve gone this far in the series without discussing what was probably the single most important component of Obama-era Education Reform: the large-scale effort to shift teacher compensation and teacher evaluation from a system that was very focused on seniority and credentials to one focused on teachers’ measured ability to generate learning gains for students.

Obama was not only convinced by this strategy on the merits, but his administration was also empowered in a very unusual way to implement this change.

This was in part thanks to the Great Recession, which left state and local governments short on money and the macroeconomy in need of fiscal stimulus. The American Recovery and Reinvestment Act allocated money for a grant program called “Race to the Top” that, instead of giving federal money to school systems based on some formula, granted funds based on the extent to which schools implemented Department of Education-approved reforms. It was also in part a somewhat peculiar legacy of the original No Child Left Behind law, which deliberately gave states unrealistic proficiency targets and required non-compliant states to obtain “waivers” from the federal Department of Education.

The nexus of RTTT and the NCLB waivers gave Arne Duncan unusual influence over K-12 policy (which is typically more of a state and local matter), and Obama empowered Duncan to wield that influence fairly aggressively — especially to push states to adopt quantitative teacher evaluation systems.