I think some of the experiences on this thread are dreadfully sad. We are are only at the beginning of all this but, in a single-form entry school, most people have had no parties, class parties or single-sex parties, which, to my mind, are all fine. There have been a couple which, either, selectively, invited a mixture of boys and girls (about half the class) or about half the girls, about which things were more
(I have to confess to some discreet texting to discover if DD1 was the only ones not invited).
In DD1's class, there is a little boy who (and no one knows why) doesn't ever go to parties, but we still invite him.
In DS1's class, there is a child who appears to have substantial needs (arrives (pre-arranged) five minutes after school starts, leaves at lunch, wears reins out of school) who was invited to our whole-class party. We are only a few weeks into Reception and they declined the invitation so I only met the mother after the party, due to the above. However, he would have been very welcome and we would have done all we could to help him enjoy it.
Perhaps it is the BF-ing hormones, but I was very weepy reading some of the above (and horrified at some of the parents). Yes, life IS brutal, but I hope I can bring up my children to be considerate and empathetic to others (and secure enough to shrug-off petty rejection). Kudos to the mother of the 6 year-old up-thread who took a principled stance.
Oh, and when all other explanations fail, I have (in a slightly different context) had to say that I don't understand why So-and-So said such-and-such and that people can, sometimes, be rotten and mean and unkind for no apparent reason and it was best just to realise that and leave them to it. Horrid for DD, but, I hope, a lesson she will learn so she treats people courteously and can measure people for their real worth.