He has ringbinders to fit in plus PE stuff. Is there a messenger bag big enough? I told him to ask his friends where they get theirs but he won't. He's using a backpack at the moment but it's feeling the strain.
I bought DS a new laptop bag from Asda - for £8. That is quite large.
DS uses a backpack - it's a Targus laptop backpack (Asda again!) he gets hisringbinders in there okay, and a packed lunch. However on the days when he has games and has to fit in size 13 footie boots(!) he uses a sports holdall - they are larger, but not so easy to carry.