I don't like the idea of 4/5 year olds being treated differently to the rest of the school. The reception class are fully paid-up school children and should be included, not separated, by any sort of behaviour. I despise all segregation.
TNO comments that children who have not reached puberty are not sexual beings. By that argument would she have 15 year old girls who have not started periods and have flat chests doing PE in just pants? I think not.
Personally I think that it is easier to teach children about socially acceptable behaviour from the time they join the school, rather than later. I certainly wouldn't expect a pre-school to ignore my 2yo's hitting & snatching - just because they're innocent little toddlers.
I'm very happy for those who did PE in their underwear and had no problems with it. Good for them. But it doesn't mean they can rubbish other peoples experiences or accuse their DCs of having 'unusual behaviour'.
'What was good enough 30 years ago blah blah'. Oh please! We'd all be giving birth on our backs on a busy ward, hygienically bottle-feeding and not using car seats.
Latest guidance says children should be in PE kit. Teaching respect for self is not just for calming the hysterical fear of paedophiles but learning important life skills - like saying no to pushy boy/girlfriends, and I've read enough threads about that on MN to know that the majority would welcome such confidence in their DCs.
Most reception age children can change clothes themselves. Learning to get changed, hang clothes up etc is just as important as doing star jumps and besides, they're hardly adhering to a strict time-table.
And lastly. Our school hall is bloody cold and we have enough coughs and colds from September until April without encouraging more thankyouverymuch.