I think this is misleading. There simply are not enough teachers in the us, largely because in a relative sense the pay is low.
It’s easy to point the finger at unions- mostly because it is a narrative that has been pushed hard for years.
The issues are way larger than the person in front of the classroom. Bad teachers don’t help but thinking I can just take test data at the end of the year and figure out which teachers are bad is wildly useless