At 7 or 8 or 9, yes, kids should take responsibility for having the correct kit for swimming / sport / ice skating.
But at age 4?
My DD's Reception class went ice skating today. As requested, I supplied padded ski trousers, padded mittens, thick woolly socks and a complete change of clothes for afterwards. However, DD forgot the kit bag. Left it on her desk. Got to the rink and discovered she had no kit at all so had to "skate" in normal school clothes (leggings, tee shirt, normal socks).
Picked DD up at 4.15 and the teacher told me she had cried an awful lot. Cried non-stop in fact because she did not have any kit, was cold and wet. Teacher said to me, "but don't let her opt out next week. she needs to get back in the saddle next week and give it another go even if she did cry a lot today"
AIBU to think that the teachers / TAs / parent helpers should have checked each child had their kitbag with them?
FWIW, I have volunteered to be a parent helper next week.