The Supreme Court will soon issue an opinion in the Janus case, which will have a big impact on unions if Janus wins as most observers expect, by reducing their membership, revenues, and political power.
Janus belongs to a union. He wants the benefits the union negotiates but he doesn’t want to pay dues. He says the union has political views he does not support. But the political activities of the union are not supported by Janus’ dues. No matter. Corporations and rightwing zealots have tried to squelch the labor movement for decades. They have nearly succeeded in the private sector, and now they are targeting the public sector. If they get what they want, working people will have no political power, and big corporations will exercise their influence solely for self-enrichment, with no countervailing power for their employees.
Why do unions matter in education? They give teachers a voice when decisions are made by governors and legislatures. Absent unions, Teacher voice will be squelched, and no one will advocate for adequate funding of schools and better working conditions.
In 2016, I noticed that Eunice Han had published a peer-reviewed study about how unionized districts improve student achievement. I posted an interview of Professor Han by Jennifer Bershire. The study appeared in 2016, and it remains relevant today in the midst of teacher protests around the nation.
Eunice Han, a professor of economics, determined that the presence of unions enhances teacher quality and student achievement, contrary to the myth that unions protect “bad teachers.”
”This study offers a simple two-period job matching model linking teachers unions to both voluntary and involuntary teacher turnover. The model predicts that teachers unions, by negotiating higher wages for teachers, lower the quit probability of high- ability teachers but raise the dismissal rate of underperforming teachers, as higher wages provide districts greater incentive to select better teachers. As a result, unions help the educational system reach an efficient equilibrium where high-quality teachers are matched with high wages. The unique district-teacher matched panel data for 2003-2012 enables me to use within-state and within-district variations, as well as instrumental variables, to identify union effects on teacher turnover. The data confirms that, compared to districts with weak unionism, districts with strong unionism dismiss more low-quality teachers and retain more high-quality teachers. The empirical analysis shows that this dynamic of teacher turnover in highly unionized districts raises average teacher quality and improves student achievement.”
In brief, unionized districts have higher wages, less teacher turnover, and a strong incentive to select better teachers.
Diane Ravitch's blog 
Too many of the citizens of this country have been FOOLED by the marketing lies of the deformers who “PAY To PLAY.”
My guess is that Mr. Janus thinks that having his name on a US Supreme Court decision that the billionaires like is a better paying gig than any benefits the union got him.
Many unions contribute to their local communities as well by sponsoring student scholarships and volunteerism including responding to natural and man made disasters. Unions also often play a role in teacher training and in offering in-service courses.
Without my union, I would be fired for good teaching because I refuse to buy into Common Core, test prep, standardized interim assessments, computerized curriculum, “close reading”, formulaic writing, teaching history without context as skill instead of content, and so on. I would be fired for having knowledge and experience (for being too close to collecting the pension in which I have invested my adult life). Without my teachers union, I would have been fired for being a good teacher.
It’s hard to say this without sounding a little pedantic (so I’m apologizing in advance), but there’s one minor correction I have to offer.
Union folks, including myself, have been sloppy about conflating the terms “dues” and “fees” in relation to the legal argument in the Janus case for a long time. It’s really important, I think, to be clear that non-members DO NOT pay dues. They pay agency fees, or “fair-share” fees.
The reason it’s important to keep this distinction in place is that erasing it has allowed anti-union folks to get away with arguing about things like “compulsory union membership” (which is flatly illegal and never exists). Closed shops don’t require union membership. They do require agency fee payments. Those payments are lower than the dues we members pay, which makes the claim that non-members money is being spent on political speech even less logical than it already was.
Again, I realize that distinction sounds trivial to most people, but the reason Janus and others have been able to get this far in their attacks on worker power is that they’ve been able to hide behind sloppy thinking even among union members and advocates.