Unions are selfish

and stuff.
Or so Megan tries to claim in a weaselly way,

A couple of days ago a commenter asked me why we couldn't just cut a deal with the teachers unions: higher pay in exchange for surrendering control over work rules. As it happens, I think that would be a very good deal; I don't see how we can get top notch teachers by turning them into underpaid civil servants. I also don't think we can cut that deal.

The problem is, the union sits in the middle of that transaction. And for the union, this is an unambiguously bad deal. They don't get a commission on the higher salary they win for their members. And dismantling all the dispute-resolution and work rule apparatus would substantially slash their power. Problems like this are the reason that the West Coast ports couldn't cut a deal with the longshoremen to pension off the current workers at full pay in exchange for the elimination of their jobs, even though my understanding is that this is one of the options they explored. Full pay for no work would have been a great deal for the membership, but a death blow for the union.

This is a whole bunch of really fucking stupid. The proposed deal would not be a good thing for teachers, because it's a bullshit trade off. Teachers face a myriad of directly competing pressures as is, the last thing they need is to lose any hint of autonomy in their own classroom. There's some jargon at play here, so I might be wrong, but this sounds like another veiled attack on tenure, which any teacher in the world will agree is worth a great deal of sacrifice to protect. Tenure is the only reason truly gifted people have to want to teach; it offers certainty. Low wages, but certainty in them, at least. Take that away, and all that remains is altruism, and maybe masochism.
Now let's step away from the specific case of the teachers' unions to a more general question about the nature of unions. Do they really put their own wellbeing above of that of their membership? Megan certainly thinks so, just like opponents of unions for over a century. Fortunately, we know she's seen season two of The Wire, so Frank Sobotka is available as an example to help explain why Megan is wrong. Let's say Frank's local IBS was offered that deal, where for not working all the union members would get a continuation of their current wages. Only the most senior of the members were able to live off the wages they were making, which is to say, it'd fuck the next generation, who were largely the children of the senior members. Unions, having a greater sense of history and duty of one generation to the next than the average American, are full of men and women who want not just good wages at good jobs, but continuity of culture and community. Frank Sobotka wanted to maintain a place for his family and people in Baltimore, it wasn't about the money, and that, Megan, is what you're incapable of comprehending.
Unions see themselves, rightly, as the last home of the blue collar worker in the US. It's not just about dollars, it's about a way of life, and if you can't respect that, your whole perspective is whack.