>adjunct teachers at universities

There is a glut of adjunct candidates with a PhD and a postdoc who can't get TT but there are relatively few with teaching degrees. The oversupply of adjuncts happens because they are the unsuccessful seekers of a much better job -- tenured professor -- but there is no similar situation for teachers. The economic analogy therefore won't fit, because the supply of teachers will respond to price signals more than the supply of adjuncts.

Indeed, but the requirement for a teaching degree is actively defended by the union, and is on a tenuous footing. It's not required for private K-12 schools, where pay and benefits are in fact drastically lower. The government of my state (Wisconsin) has moved to relax teacher licensing requirements for public schools.

When I was an adjunct, I had no interest in getting onto the tenure track, or in teaching as a career. I was simply new in town and needed a job.

I don’t think unions are necesssry, the less attractive teaching is because of the (false) promise of pensions, the fewer people will be willing to enter the profession - forcing wages to rise.

On second thought, what will probably happen is that they will flee to private schools, the more affluent will lobby for “private school tax deductions” and leave only the worse teachers in public schools and only the less affluent will go to public school.

So logically thinking your conclusion through, why are unions not necessary then?

are the unions really helping now? The unions are forcing the government to make unrealistic promises. The government is kicking the can down the road and the taxpayers aren’t willing to pay more in taxes now to either fully fund the pensions or pay the teachers more to make the profession more attractive without the promise of pensions later.

Everyone is complicit - the union, the politicians, and the taxpayers. If the unions were honest and told the teachers that the pensions they bargained for were illusory, the teachers would demand more pay now.