Oh yes, Erin. I'm familiar with those things going on. My husband and I had to do the very same thing at my stepkid's school. Sounds like your dad and my husband would get on great, because he used a lot of the same words. You see, they'd decided that she was to spend her study hall periods tutoring kids who'd failed the state test so they'd pass it next time. Unfortunately, her mother had enough say in her education that she could veto homeschooling. It had to be public school or Christian school, and in our area, believe me, the public school was the lesser evil.
Your story reminds me of another similar argument I've heard of against homeschooling. Several parents I know have been told by school employees when they withdrew their children, "But our school needs students like your child!" Interesting idea, isn't it, that the students exist for the benefit of the school and not the other way around? Of course, we know that, but you don't expect to hear it said outright like that.
So yes, I suppose that losing intelligent students who do the teachers' jobs better than they can and can be coerced into doing it could possibly result in worse conditions for the remaining students. Somehow, though, I don't think that's quite what the writer meant.