In the early 1990s, the logic and policies of systemic reform launched a press to coordinate the pursuit of excellence and equity in U.S. public education, with each other and with classroom instruction. There was little in that policy moment to predict that these reforms would sustain, and much to predict otherwise. Yet, nearly three decades hence, many public school districts are working earnestly to pursue the central aims of the reforms: all students engaging rich instructional experiences to master ambitious content and tasks at the same high standards. That begs a question: What happens when new educational ambitions collide with legacy educational institutions--not in a policy moment but across a historical moment? This chapter takes up that question by reviewing the rise of mass public schooling in pursuit of universal access, a historic pivot toward instructionally focused education systems in pursuit of excellence and equity, and changing patterns in instructional organization and management that follow. The lesson we draw is that, even amid incoherence and turbulence in education environments, sustained public, political, and policy support for new educational ambitions opens up new opportunities for those ambitions to manifest in the structures and the work of public school districts.