Sarah Schenirer AH did not go to any professional school. Neither did Rebbetzin Kaplan AH.
The problem is that some teachers, male and female, are in chinuch as employment of last resort. They lack dedication because they fell into chinuch rather than wanting to go into it, or they burn out because of low, late salaries and discipline problems (and parents telling their kids that their rebbeim and teachers are losers who could not find real jobs.)
I think the frum world needs a teaching corps, where the community pays schar limud for yeshiva or advanced seminary as well as perhaps professional training in exchange for a 5-10 year commitment to teaching.