Plus, education for 7 years makes no sense if you expect to live another hundred; muggles spend 1/5-1/6th of their life in education, but wizards only 1/15th

This, at least, does not confuse me. It's not like this is a historical constant, for most of human history most people have spent less.

Anyway, it's implied that vocational training exists after one is finished with one's mandatory education.