NEW YORK (AP) — Former President Donald Trump has called for parents to elect and fire school principals. Florida Gov. Ron DeSantis has banned instruction on sexual orientation and gender identity in kindergarten through third grade. And Nikki Haley, the former United Nations ambassador who is expected to announce her White House bid next week, is among the cadre of contenders who have taken aim at critical race theory. In the opening stages of the Republican presidential primary, lessons for school children are emerging as a critical flashpoint.