Some concealers are really good at covering the discolouration of self harm scars/ cuts, I use concealer and foundation and then wear bracelets. You can get this really good concealer that is used to cover up burns as well I think.
You can get really lightweight sheer tops that are made to wear in summer, they are just as cool ad wearing no sleeves, or wear lace sleeves or something like that (if you don't have a school uniform).
Hope this helped a bit
