When your kid is the only one excluded from a party

Just learned that there is a party next week for a classmate of my kid. Every kid in the class was invited except for my kid. The invitations were handed out at school (put in the kids' cubbies).The girl told others that she didn't want to invite my kid because he refused to obey her "be extra nice to me for 3 weeks in order to get an invitation to my party", and was just "regular nice" to her. We heard this from the parents of other kids in the class. I have no idea why her parents agreed to exclude 1 kid from her party.Unfortunately my kid will hear about this party from his classmates. Not sure how to handle this...he thinks every classmate is a friend. via /r/Parenting http://bit.ly/2XiZgs5