My daughter is 15 and is in high school. She is well like from the students, but she is having trouble with an associate principal, who is so mean,he used to be a cop I guess so he likes to talk to these children like criminals. Well, my question is should they be allowed to call her to their office and try and persuade her to drop out? They even call her sister down and ask her to ask me. She is mouthy but that's it, no drugs, no smoking, no nothing from her. Ihave a court appointment because he charged her with out of control behavior, What should I go in and say? Oh, and she was also diagnosed with ADHD a month ago.

You need to get a lawyer and prove they are treating her wrongfully or be prepared to drop her out and home or cyber school her.
My kids have had some problems like this with some teachers through the years and it is hard to prove them in the wrong because they have their upstanding reputation and you, her and anybody else is just the target.
Most states it isn't even legal to drop out at least until 16 or 17 so their harassing her like that should help some.