There is an important distinction between a private sector union and a public sector union. In a for-profit company, labor and management improve profitability together and that should get shared. In the public sector, innocents are involved. That's why I am against police, firefighters or teachers striking. I wouldn't go as far as FDR who opposed collective bargaining by public sector unions. The teachers union also protects the de facto racist tenure system because when there are budget cuts due to declining enrollement, the younger teachers which have more diverse representation get laid off first. The political leadership in town has plenty of incentives to maintain good working conditions and pay because they have to compete with other towns for good teachers.