An excellent summary by Thomas . DiLorenzo:
The enormous power of government-employee unions effectively transfers the power to tax from voters to the unions. Because government-employee unions can so easily force elected officials to raise taxes to meet their “demands,” it is they, not the voters, who control the rate of taxation within a political jurisdiction. They are the beneficiaries of a particular form of taxation without representation.
In my locality, the school unions dominate all local politics, up to the district’s Representative to the House, and nearly all of my property taxes go to the schools.
Which means, if I can’t or don’t pay the property taxes, the school will have the police seize my home and sell it to someone who will.