That's an American problem though. In most of Europe you need a masters degree to teach highschool and that involves at least an undergrad level of understanding the subjects you will teach.

E.g. in Hungary I had a university CS professor that originally wanted to be a highschool teacher and a highschool physics teacher that originally wanted to be researcher. Their choice of degree didn't determine which outcome they got. The researcher and teacher curriculum had an 80%+ overlap.