Mean girls start early. Need advice

My daughter (6) is friends with two girls in her class. We carpool with them 3 days a week. About 2 months ago, the two other girls started ganging up on my kid. Just little annoying things, like pretending they didn't hear her when she was talking to them, or the two of them taking off immediately when they all got to school, leaving her behind. They did this enough times, where we texted the other parents and let them know what was up. We really like both girls' parents a lot, and the parents agreed to talk to both girls. They did talk to them, but nothing has changed.They have been upping their "game" lately. Still doing the previous behaviors, but are now discussing their day;s plans in the car, and making sure my daughter knows she is not welcome to join in. They make little clubs during recess and tell my kid she can't play with them. They have told other girls not to play with my daughter.In class they also snub her and ignore her. My advice so far has been to ignore them when they are being assholes and find someone else to play with (which she does). My kid is really sweet and never wants to hurt anyone's feelings. It wouldn't occur to her to be deliberately mean. When she plays with either of these girls individually, it is usually fine, and they have fun. It is only when they are in a group of 3 that these two gang up on her with the intent to exclude her and make her feel bad.My husband and I have decided that we no longer want to participate in the car pooling. I don't see any benefit in having my kid end up feeling like shit three days a week before she even gets to school.My question is this: What do I say to the other parents about why we no longer wish to carpool? They will have to make other arrangements for the day we drive, and I don't know if we need to give them an explanation why. I don't want to go the route of "your kids are assholes and picking on my baby", when it is more like "my kid shouldn't have to endure being treated like crap if she doesn't have to be".Any advice? via /r/Parenting http://ift.tt/2gqfuKy