Are public schools allowed to teach creationism?
Allowed by whom? Are you under the impression that there’s some overarching national authority that decides what public schools teach? There isn’t. Public education is a state matter, and each state decides curricula, selects textbooks, sets criteria for teachers and tries to figure out how to improve schools. Below the statehouse there are local (county, city) school boards with greater or lesser decision-making power left them by the state, and even in a particular school, though everyone is supposed to be governed by policies announced upstream, there is usually some day-to-day flexibility, depending on how far into micro-managing the curriculum the authorities have gone. And the farther down you go toward the actual classroom, the more impact an affinity group of some sort with a fixed agenda can have. There is, however, the Constitution, and a lot of people are intent on maintaining freedom of religion or its absence and the separation of church and state, and they usually succeed
