I had a discussion with DS1 (Yr 1) the other day about why he wasn't allowed to walk to breakfast club at school by himself yet X (who is in Reception) is - I was a bit stumped tbh about how to justify it 
The reason is that I don't think DS1 is old enough to do it by himself yet (the door to breakfast club is right round the back of the school) whereas X's mum thinks X is (which I don't have a problem with at all) but not sure how I can justify it to DS1 who is very hung up about people's ages and what they can do!