Our reception class had a classroom assistant, and I've always assumed she gave a hand where needed (perhaps wrongly - but there you go), but you should ask if you have any concerns about it. Otherwise you'll just worry!

By the age of 4 they should be fine getting on and off the loo and wiping their wees for sure! A lot of children wont want to poo at school so will hold it till they get home. Maybe encourage your child to give it a go at doing everything herself and then you check.