On a weekend day in the summer of 2020, President Donald Trump phoned his education secretary, Betsy DeVos, out of the blue. DeVos’s focus that summer was the mass disruption the pandemic had inflicted on students, but Trump was worked up about something else: the 1619 Project, a set of essays published in the New York Times that centered slavery in understanding the founding of the nation.In a “rant,” DeVos recalled, Trump wanted to know how the administration could ban it from classrooms.“I had to remind him that the United States does not have a national curriculum, and for good...