PART of what happened to the schools was womens' lib. Before womens' lib, really bright career-minded women became nurses and teachers and secretaries. Now they become doctors and lawyers and accountants and engineers.
The people who become elementary school teachers are either the ones who really really want to teach, or the ones who want to go to college, but can't pass in any other major. The latter are PART of the problem. (Secondary education is tougher, because you also have to take subject-matter courses.)