Good teachers don't need tenure.
Tenure's not about protecting "bad" teachers; it's about protecting good teachers. What would happen to teachers without tenure? They could — and would — be fired for virtually any reason.
It's not hard to imagine teachers being dismissed because they failed the daughter of an influential businessman or because the school board president's nephew needed a job.
In these fiscally troubled times, what would stop a school board from replacing a veteran teacher at the top of the pay scale with a first-year teacher — simply to save money?
Tenure is the first line of defense against attacks on academic freedom. Teachers can engage their students in a free exchange of ideas only if they are protected from arbitrary dismissal for doing so. Tenure prevents school boards from arbitrarily dismissing teachers for holding political, religious or social views with which they disagree.
It protects academic freedom the way the First Amendment protects freedom of the press.