A parent recently asked me a question about this and I would like to clear up any confusion that may exist about birthday party invitations. The school rule is this:
If you want to send the birthday party invitations into school for your child to hand out, you must either invite the whole class or if your child is a girl, invite all the girls or if you child is a boy invite all the boys.
Teachers will not allow your child to give out the invitations in school if this rule is not followed.
This rule only applies when you want your child to bring the invitations into school to hand out. You are certainly free to invite anyone you want to your party, but please do not send the invitations into school to be handed out if you are not going to do one of the above.
I hope this helps. :)