This is a point made in the Documentary, namely, that tenure was created as means to protect academics from reprisals from their administration simply because their research might prove to be controversial or difficult for the public to accept. The process to achieve tenure in both the US and Canada is long and difficult while in the US public school system (according to the doc) "you have to maintain a pulse for two years" and you get it.

So I agree with velvetpage that teachers need protection-- not sure that it should be automatically granted. It should be possible to turf a clearly bad educator while at the same time not be a method for pernicious parents to persecute teachers they have a beef with.