Teacher's Unions aren't perfect and there have been some valid complaints about them, but that's basically every union. Honestly, my biggest complaint is that teachers have unions and they're still not paid enough.

But at any rate, this is typical conservative rhetoric. "We've found (or invented) one thing we can complain about, so rather than having a rational, calm discussion about the state of things and how we can improve that thing, we want to cause the most drama, scare everybody the most, and tear everything down, while promising to replace it with something better, a promise that we'll never, ever, in a million years, deliver on."