I may be painting with a broad brush, but I've seen way too many teachers with an attitude, an expectation that they have unlimited access to parents' time, and money. Booster clubs, "write-a-check" programs, etc. If you don't acquiesce, the clear message is "you don't love your child."
I've got news for them: they can KMA. I've done two things for my 3 children (30, 28, and 15) that they can never take away from me: I made sure they were born in Texas, and I taught them how to swim.
Anything else is gravy. lol