California parent of public school HS students here. It takes two years to get tenure in CA. That's just not long enough.
There are some cheap, inexperienced, (and bad) teachers with tenure. Overall, I'm very grateful for most of my children's teachers. But this year one of my daughter's teachers was clearly completely incompetent: young, arrogant, lazy, and intellectually vacuous. We complained to the principal (we were not the first to complain). Their hands are tied. It's almost impossible to dismiss an incompetent, tenured teacher.