13 yo isn't very interested in clothes, his main criteria are that they're comfy and he doesn't have to go shopping.
I generally get him stuff from Next or M&S (no imagination!)
However, he's tall and skinny. For school uniform he has age 14/15 with an adjustable waist but for other clothes, the largest kids sizes are not long enough and small mens' things are far to wide. He's far from the only young teen built like him, so what do others do?