It’s one of the school dress up days I don’t mind.
Evacuee/Tudor/Greek/Roman/around the world/etc are all more annoying for clothes that can’t be reworn.
My eldest has had 3 Christmas jumpers in total. She’s still wearing the most recent one - 3rd year now.
Middle child has had 2 jumpers (one of which was her sister’s hand me down), and 3 t shirts, which all still fit (last year for 2 of them, sadly)
Youngest has had a few t shirts, which still fit, and 3 jumpers, 2 of which still fit.
So, across 6 years or so, and 3 children, I’ve bought 7 jumpers, 5 of which are still being worn. Not exactly excessive.
My dc have also chosen well, and are happy to wear their jumpers and t shirts for most of December, so they are not worn just for one day.
I can understand the problem with children from families who cannot afford specialist clothing, but that’s not restricted to this one dress up day at school - there’s so many, often requiring weird and wonderful combinations, or last minute homemade alterations to existing clothing etc. it’s hardly a new thing.