The notices to parents began arriving fast and furious in the weeks after the death of George Floyd in late May. In dramatic, urgent language, K-12 schools across the country – both public and private – professed solidarity with Black Lives Matter and vowed to dismantle white supremacy, as they scrambled to introduce anti-racist courses and remake themselves into racism-free zones. The president of the Lower Merion School Board on Philadelphia’s affluent Main Line declared to families: “We need to eradicate white supremacy and heteropatriarchy in all of our institutions.” In Maine, a coastal public school district where 3.7% of...