Their union won’t let you pay a new hire more than a less competitive teacher with more seniority. Therefore almost nobody with the capacity to work at a FAANG will choose to become a high school CS or Math teacher earning poverty wages.
whats that supposed to mean?
For example, hiring a CS or Math grad as a HS CS teacher is more competitive than hiring a French Literature grad as a HS French teacher. The CS grads have a lot of other options and at any fixed compensation you will get much better French teachers than CS teachers.