Carrot AND stick, people, carrot AND stick...
#1. You MUST raise teacher salaries. The folks who can get jobs elsewhere, are, unless they love it too much for their own good.
#2. You MUST hold teachers accountable via some mechanism. Otherwise you get teachers like Mr. Hopkins, my Japanese teacher who passed me with an A 3 years straight, although I never quite got down the Hirigana/Katakana, let alone the first 100 Kanji... And couldn't even conjugate verbs properly.
All he cared was that I played a decent game of Shogi.
So, raise salaries, (which will increase the pool of applicants) and then get rid of the ones that don't produce.
Do both at the same time.
You done bitching at each other? Good.