Well if the situation is the same as when my son got his teaching credentials, a lot of his fellow students had a very difficult time getting jobs because the older teachers wouldn't retire. So if that has remained the same it's just another slap at legal immigrants and Americans!
They go after a lot of teachers in their fifth year of teaching or used to because they vested in the pension plan after completing their fifth year. Hence the shortage. Treat the teachers horrible and people don’t want to teach there and leave.