Jeni-

I think many schools also tend to be dismissive of single parents, moms in particular. You might consider going in to a meeting with a male friend who you can identify as an "advocate" for your child. He doesn't even have to say much, just take a few notes and look deeply concerned. It seems that the principal is just trying to intimidate you. Intimidate her back! If you have a lawyer friend, that would be even better...