[user104658]

The specifics of what he's wearing are irrelevant... all that matters is whether or not they otherwise allow dress-up. If dress up is allowed (e.g. spiderman costumes, doctors / nurse costumes, girls wearing princess / fairy costumes) then there should be no problem with him dressing as a princess. He's just a child. It doesn't mean anything. When I was young, my parents had friends whose son liked to dress up as a fairy. Constantly. I remember finding it weird but... he loved it :/. 20+ years later, he's a perfectly normal (and straight, I should mention, not that it should matter) guy.

My daughter plays "Frozen" with the little boy from next door who is 6, and he usually plays the role of "Anna".

There's nothing wrong with cross-gender role play... it doesn't mean anything and it won't "cause" any confusion.

So like I said, it SHOULD just be an issue of general dress code. If fancy dress (in general) is disallowed, then obviously he shouldn't be dressed as a princess. If it is allowed, then there shouldn't be a problem. There's no right or wrong answer there as it's down to the individual group. Josy mentioned kids having to wear uniform to playgroup... I also live in Scotland, and my daughter's pre-school, which is part of the actual primary school not even an external organisation, has a completely open dress code. 90% of the time my daughter just wears her day-to-day clothes but she has in the past gone in as tinkerbell, a doctor, a nurse, a pirate and a cat (including whiskers!).

So there's clearly a lot of diversity between different groups as to acceptable dress. Can't really pass judgement on this story either way unless we know what ther reaction would have been to him arriving in "boy" fancy dress, like a fireman or pirate. If it would have been the same then the mum is clearly kicking up a fuss over nothing and making it into something it's not. If it would have been fine then the playgroup has outdated ideas about what's "OK for boys and OK for girls".