It is possible to have a proper balance between teacher's associations (not unions) and the school administration. We have it here in Nebraska. My wife was the president and chief negotiator for the local association for a few years. They have a contract which is fair to both sides and have not had a "strike" or "dispute" for over 5 decades. Incidentally, both she and I are conservative voters.
Incidentally, these associations got started in the 30's when married teachers were being let go because they had a working spouse at home and one paycheck so a single teacher was kept instead. Hiring and firing was not being done on a merit basis.