If you truly feel that this is a case of discrimination do what your are already doing, continue trying to shed light on your situation; have you talked to the school board?, the one thing that difinitely won't help is your daughter or you acting out against the discriminators, the collecting of imformation time,place,when, where etc, is important and witness or others who have been discriminated against also is very important, you along without witness to the situation will be hard but not impossible: Dr. Martin Luther King Jr. once said
Darkness cannot drive out darkness; only light can do that. Hate cannot drive out hate; only love can do that.