A Cinderella Story/Headscratchers

Cinderella, in this case, has her own spacious fully decorated bedroom, her own computer, her own car, a cell phone, lives in a house in an upper class neighborhood, and goes to a school filled with similarly upper class kids and, therefore, gets a lot of funding for clubs and stuff. Her main source of misery is that she has a steady job in her "wicked" stepmother's cyber cafe. Plus, she's a senior in high school and has excellent grades. She would only have to put up with her horrible relatives for a few more months before she undoubtedly goes off to college with a couple of scholarships under her belt! Most other versions of Cinderella would kill for a life like this!
- Her mother specifically lied to keep the diner away from her and keep her out of college, so dependent on her. As bad as the other Cinderellas? No. Bad, as compared to the lives of the target audience? Yep.
- Plus, I am pretty certain that the end of the movie said that the stepmother was breaking child labor laws through the terms of her employment to her stepdaughter.
The movie's message of sticking up for yourself has good intentions, but it is a horrible message to send to kids who are abused at home like Sam. Sticking up for yourself will just make things worse for yourself (realistically Fionna would have probably beat Sam or threw her out on the streets for mouthing off to her in the end), and kids who are in that position should look for help in external forces (a nicer relative, or the police). It also has the Unfortunate Implications that it is a child's own fault they are abused ("because they are too weak to stick up for themselves.")
How the heck did those cheerleaders not get punished for the pep-rally where they publicly humiliated Sam? Honestly, this really pisses me off.
- I think the cheerleaders and Sam's stepsisters not getting their comeuppance was the least annoying part of that scene.
  - Maybe it varies by school (though I doubt it) but wouldn't who ever was in charge of organizing the pep-rally have to supervise what would be shown at said pep-rally? Logically he/she would have to approve everything to make sure it isn't inappropriate. So does this mean a teacher knew they were going to humiliate Sam and just let it happen?
  - One teacher is seen looking upset about what is happening (the woman sitting behind Austin) as if she knew someone was being mocked yet at no point did she or any one of the teachers present say anything at all to stop it. They never discipline the girls afterwards when they see they hurt an innocent girl's feelings.
  - The skit they do to humiliate Sam is not funny (and not just because we, the audience, sympathize with her). It was painfully unfunny yet everyone is seen dieing laughing at it. Then afterwards when it is revealed by Shelby that they are mocking Sam the entire student body keeps laughing like its somehow hysterical and even start chanting "DINER GIRL". Why? It's been awhile since I've seen the film but I'm pretty sure that at no point is it established that they all dislike her. She's just an outcast as far as I remember and only Shelby and her minions dislike her because... well... they're horrible. Why is the entire student body suddenly being so cruel to her? It just makes no sense to me.
I will admit I haven't seen the entire film in awhile but to my memory other people knew about the abuse Sam was suffering at home. (Please correct me if I'm wrong) Carter, Rhonda, and other minor characters at the diner seem aware of what her home-life is like. So if they all know, why didn't anyone do anything to try and stop? Why did't anyone callSocial Services?