Comment by rtkwe

> I've always found it weird that you need teaching certification to teach basic concepts to kindergartners but not to teach calculus to adults.

I think this is partially due to the age of the students, by the time you hit college the expectation is you can do a lot of the learning yourself outside of the classroom and will seek out additional assistance through office hours, self study, or tutors/classmates if you aren't able to understand from the lecture alone.

It's also down to cost cutting, instead of having entirely distinct teaching and research faculty universities require all professors to teach at least one class a semester. Usually though the large freshman and sophomore classes do get taught by quasi dedicated 'teaching' professors instead of a researcher ticking a box.