I don't question his love for his daughter, but in a case like this, perceptions can be more potent than reality. If she perceives him as not caring, not believing her, or not protecting her, she will still be hurt. A parent can love their child to pieces yet not realize how much a given situation hurts them.
You mentioned before that he's not really the touchy-feely sort, but could he take her out for a drive and talk and tell her that he might not express himself well, but he will always listen to her and always be there for her. Even if this is awkward and uncomfortable, it would mean the world to her.
Those school administrators are blithering idiots, and if they are indeed holding her back to help their ratings, you need to get both kids to a different school in a different district. This is unconscionable. A principal who would allow this would be all too likely to brush a sexual assault aside to protect his/her school's reputation. I understand not wanting her to miss the trip, but I'd at least start the process of transferring them to a new school.
I agree 100% with those who have said grabbing a breast IS SEXUAL ASSAULT, not boyish teasing.
In addition to helping Becca, has the school considered that a boy that young grabbing a girl's breast NEEDS SERIOUS HELP? Hello -- this boy is a sexual predator in training. If nobody acts, they are enabling and, in fact, encouraging him. For this reason if none other, I would report this to the police. Having his victim's grandmother give him a stern lecture isn't going to help one bit.
As for the boy's family getting evicted if enough people complain, this could be a VERY good thing, as he *might* see that his actions have hurt his family, and they *might* take this issue seriously.
I'd be very curious to know if he has assaulted or bullied anyone else, or if he has been in any other trouble?
Amanda, I feel so strongly for Becca, and I'm so glad to hear that she and her brother are taking martial arts classes, as well as the other activities. You are a great mother and I empathize with your position as new member of the family. Keep fighting!