[rwmj]

Individual private tutors (in the UK at least) need a background check if they teach children under 18, but not a license. Teachers of whole classrooms in schools need a QTS, which is a qualification demonstrating their skills as teachers. This seems reasonable since it gives a fairly simple way for parents and schools to evaluate whether a teacher is completely useless or not (but not that they are a great teacher - a license probably could never tell you that).

I'm interested to know why you (I assume) think licensing teachers is a bad idea.