The Substitute trilogy adopts a noble cause. All three films endeavour to teach their audience the great value of violence. The technique is very subtle. The films begin with a school where it seems that humourless criminal thugs have taken control. They bully students and even the teachers, to the point of making their lives a living hell.
Substitute 3 sticks to the formula. That's where Treat Wiliams steps in, fresh from serving as an honourable mercenary on the good side, of course, in some war. (His salary is never mentioned. Perhaps he just does it for the satisfaction of knowing that he is killing bad people. I always feel satisfied when I kill bad people, so it would make sense.)
His problem is not the bad thugs in the school. He can smash them to a pulp with very little effort, and he takes every opportunity to do so. The trouble is that the pretty blond English professor isn't yet convinced that the solution to violence is more brutal violence. It's probably all those arty books she's read. Therefore Treat has to demonstrate by punching, kicking, knifing and shooting as many of the bad guys as possible.
I won't spoil the ending. You'll have to watch the film yourself to find out whether the prof sees how misguided she was.
