Premise: Youngin me - Turnarounds WIP

Just wondering how to improve these before adding colour? I feel like the front back sketch needs to be improved the most, I think his arms look weird probably his elbows and his hands need to be changed. A few more tweaks like matching up the height of certain parts will be changed. The colour on the sleeve of the front sketch is supposed to be paint as my uniform was constantly destroyed in it, I did add a school logo to the jumper but I thought it was a bit of an eyesore so I took it out.