A bit of back story:
DS (7) was best friends with a boy at school. At the start of the academic year he started telling me that this child was asking him (and others) for money to be friends/play certain games with him, along with other sightly worrying, manipulative behaviour. As we knew the parents I thought I'd mention it to them when we saw them, but then ds and this kid got into a fight and the other parents complained to the school, saying ds had 'attacked' their son. On further investigation it turned out that this other child had been teasing ds which had provoked him. Ds was disciplined, both by the school and us (we don't put up with any violent behaviour), but it put us in a rather awkward position. We couldn't bring up any other the other child's behaviour as it would then look like we were saying 'well he started it' and be very petty. The other child wasn't disciplined however and has been carrying on his rather unpleasant behaviour to other children as well (like calling a sn child in his class an idiot and stupid). However, they do still play quite often and we put it down to just ordinary kid's fighting.
Ds has become more and more withdrawn and has had fewer children in his class playing with him over the course of the academic year to the point he'd now deeply unhappy and comes home saying that he's 'such a waste of space' and 'a total idiot'. We've been into the school and spoken to the head and her suggestion is that we send ds to 'socialisation' classes (anyone who has met ds would not think he needed this - he also does a lot of extra curricular activities with kids his own age and has no problems there).
However, this is all by-the-by. He still tries to play with this other boy, and they still get on for the most part. This other boy is having a birthday party this week though and ds isn't invited, though he insists they are 'best friends'. Ds says, though, that the other boy has told him that his parents have said he's not allowed to be invited because of the fight earlier in the year. AIBU in thinking that the parents aren't doing their son any favours and are teaching them to hold a grudge, and to feel angry for my son? I just feel so upset for ds - he isn't close friends with many others in his class and seldom gets invited to anything.
Sorry - just realised this is very long and rambling