Yes and no. Obviously his teacher was in the wrong for yelling and screaming at him over such a trivial matter. However, in California at least, testing standards (as dictated by the state) are incredibly strict. More than one good teacher has been fired for not following the written procedures EXACTLY. Any reported deviation (state inspectors interview students and staff at random) is grounds for punishment and possible dismissal. It's a complete disaster, but this is what the teachers have to deal with. It can be incredibly stressful.

I'm not so sure... The standardised tests don't actually weed out crap teachers as they can just teach to the test, and they do a lot to hurt the effectiveness of good teachers.

Also a lot of the motivation of the teacher who was annoyed with my parents was that I was causing problems in tests due to being interested in stuff well outside the domain of what would be taught in class.

Set tests largely test how good you are at those set tests, but most problems you will encounter in the real world are unbounded by a curriculum and the ability to recall stuff you have very recently read, while useful, is not a particularly good measure of wider ability.