Oh my gosh I am flabbergasted! That is horrific. Your poor boy.
Then she said very abruptly that she has 23 other kids and asked us what do we want her to do.
Um, Her Job? I realise there are two sides to ever story, but she sounds unable to cope with her duties at best and unbalanced at worst from this version of the story?
I would be letting her know that a) if she wants to suspend your child she needs to actually notify an adult in writing or with a phone call (not a voicemail) and b) half picking up his papers and then throwing them back down is wildly inappropriate behavior for an adult! Then I would be letting the principle know the same, most likely in writing as a formal complaint.
Note: I am assuming that schools in the US can't just suspend a child without making sure an adult is aware of the situation? There must surely be a policy about this? What if the child had just been dropped at the gate and there was no parent to send them home with?