I've thought for years that secondary schools need to adopt the same approach as primary schools.
Specify the colour scheme and basic rules e.g. skirts to at least the knee, sensible shoes, decide whether shirts or polo Tshirts etc which would level the playing field for so many families.
DD1 has to have the school logo on almost everything (jumper, polo Tshirt, uniform shorts, PE top, PE skirt/shorts, PE socks) so buying just two of each everyday item sets you back over £50, plus the PE kit on top for another £50 which inevitably gets lost stolen. That's before you buy the basic trousers/shoes/coats and necessary school supplies. It's impossible to kit her out for less than £200 after a growth spurt and that's with wear one/wash one.
DD2 in primary by comparison wears exactly the same colours but I can get hers from Asda/Tesco wherever they have items in my price range. We get her one logo polo shirt and jumper for school trips/photos, the rest is generic. I can kit out DD2 for less than £100 including coat/shoes.
There's zero justification to insist on branded items for school uniform beyond ego of the people running the school. There are massive reasons to make it a standard attainable to most families instead of a select few with the rest having to source 2nd hand where possible (not that second hand is a bad thing, but to noticeably be the child always in faded uniform isn't a pleasant experience).
I think the new measures for going back to school should insist on this to make the lives of several thousand people with lost jobs/lower income because of lockdown/the virus a bit easier in terms of making the little money they have stretch.