In recent years, justices on the US Supreme Court have made explicit historical arguments about US schools in order to promote a broader role for religion in US public schools. For example, in Espinoza v. Montana (2020), Chief Justice Roberts cited the late historian Carl F. Kaestle to buttress his arguments, but did so in a way that misrepresented Kaestle’s nuanced account. This article compares the justices’ historical arguments to the best evidence from the historical record. The essay argues that historians of education—whatever their political beliefs—can and should guide policy by providing reliable, accurate historical information.