I think you're mixing up my points. The Constitutional concern doesn't lie with tenure itself; enforcement of the Constitution would replace this rather far-fetched excuse for maintaining tenure as some holy trait. The legal system already exists to help teachers in cases where they're punished for teaching science instead of religion in government-funded institutions, since doing so already runs afoul of the establishment clause; a tenure system doesn't really add much, and (in my own observations at least) only seems to benefit veteran teachers at the expense of students and newer teachers.