It's not about understanding critical thinking it is about thinking critically.

When you write an essay to compare and contrast, or pick a position about specific subject you know that you can't use your for feeling or use some random guy on Facebook you still have to back it up if you want to get a good grade. It doesn't even matter what your position is, as long as you do work. You know the teacher won't accept any bullshit. It purposefully is also given topic that you are unlikely to know about so you do that work.

This is what teaches you critical thinking skills, that you can apply in your life in the future for new things.

People who has others do this work for them or attended colleges that didn't do this got nice disservice done as it is much easier to lie to them.