At ds1's old school, the boys had to leave their PE kits on racks round the school - they weren't allowed to take them into classrooms or the dining hall, and there wasn't room in the lockers.
It was a well-known 'prank' in the school to take someone's kitbag and move it to another set of racks, or worse, to empty it out, and strew the kit all around the school. Ds1'sw kit vanished twice - once he managed to find all the bits of kit in the various locations they'd been left in, and the second time we had to replace all his kit - and because it was a selective grammar school with expensive uniform, replacing the kit cost around £100. It turned out in the end that his bag had been dumped somewhere really obscure - it did turn up some months later, but by then, we'd already replaced all the kit, because otherwise he'd have got detentions for not being properly equipped for PE.
You had to have indoor PE kit, rugby kit (including the school's rugby socks at £4.50 a pair), a pair of rugby boots and two pairs of trainers - one pair for indoor PE, and one for outdoor. Even buying unbranded trainers at the cheapie shoe shop, replacing all this was hugely expensive, because you could only buy school PE kit in the school's own uniform shop.
I had huge rows with the school about these 'pranks' - I saw nothing funny or clever about them, and felt that the school had a certain amount of responsibility for the costs we had to bear as a result, because it was their procedures and rules regarding where kit could be left that made the 'prank' possible - needless to say I got nowhere with the school.
I'm just glad the boys are now at a more sensible school, where PE kit is shorts/tracksuit bottoms and t-shirt - the only rule being no football shirts - so the kit is far less bulky and can go in lockers or be carried round by the kids, and is far cheaper to replace if anything goes missing.
As for ties - well don't get me started on ties!! We should have at least 5 school ties in the house - but the dses appear to be completely incapable of keeping them. They don't disappear at school - but the house appears to be a black hole for ties. One day last week we could only find ONE school tie - despite my asking the boys the night before to make sure they had everything they needed for school. They assured me they did - but apparently checking that your uniform is all present and correct means assuming you know where your tie is, not actually having it in your hot, sweaty little hand (which is the definition of checking that I've tried to enforce in the past).
GRRRRRRRR
Sorry - tie rant over.