Well, this isn't university either. This is community college, and especially, the kind of class people take because they didn't learn this stuff before, or they took mathematics classes so long ago they can't be expected to remember them. It's a course meant to cover deficiencies needed so people can reach freshman levels of mathematics.

However, yes, integrals and differentiation are a long, long way off.

(Some of the students did check their results, although if they made the same mistakes consistently with a value rather than the variable x, they'd get results that seemed to check out.)