EvaReady
No Leather and denim jackets is a common rule in schools. It has nothing to do with academy branding (I remember having my denim jacket confiscated as a student) and everything to do with them not being proper coats and are more of a fashion thing.
If I look at my KS3/4 students, a third don't wear a coat (and then tell me they are freezing and wet in the rain because teen logic), most wear any other sensible coat & a tiny minority try to wear a hoody under their blazer because they prefer a hoody to a school jumper (they quickly lose the hoody).