For the benefit of the many non-Brits complaining about how unrealistic it is: the Leaving School Grounds Unsupervised form is (when I grew up at least) a huge social divider and Big Deal in a lot of British schools. There was a whole micro industry at mine where the ~70% of kids who were allowed out would provide delivery services for sweets and pop for the 30% who weren’t.
JKR didn’t just pull this whole thing out her ass, it was something that most British kids will have instantly related to. (She’s still an awful human mind)