FRANKFORT, Ky. (AP) — Teachers across the country have left their classrooms this spring to protest at state capitols, closing schools to win pay raises and better funding in mostly Republican-controlled states.

But their most disruptive act yet may well have come Tuesday night in Kentucky, where a high school math teacher who had never run for public office before defeated the state House majority leader in a GOP primary.

The upset could portend a tumultuous November general election in Kentucky and beyond.

In Kentucky alone, at least 34 current or former teachers — two-thirds of them Democra...