Having a degree in philosophy or mathematics or whatever does not automatically make someone a good teacher. Teaching - particularly with young children - is a skill that is almost orthogonal to subject knowledge.
> Teaching ability is an innate feature of human beings.
Distribution seems to follow a bell curve - you’ll usually find the people with exceptional teaching ability harnessing that aptitude in a professional setting.
All features in humans follow a bell curve. Viva la difference!
Pretty much all humans can run. Yes, some have exceptional talent at it, and some can barely walk. But the vast majority can run reasonably well. Exceptional talent at teaching is certainly not required for routine learning.
Besides, you can buy the workbooks for every level of math, and work it through with the critters. There's no special skill needed. I don't recall any teachers of mine at any level who had any apparent special skill at it.
Except for Feynman. I attended one of his lectures. It was amazing! Feynman was at the extreme end of the bell curve, that's for sure.
> At my university, I was taught by professors and grad students, none of whom had a teaching degree.
Professors and grad students may well have done a course on how to lecture. It is obligatory and/or an easy way to pick up credits in many PhD programs. In any event, grad students teaching badly, because the department has allowed the more competent faculty to put their teaching burden on grad students, is a common complaint about US universities.