Just in case anyone has 13 year old boys who are on the cusp of puberty and therefore carrying a bit of puppy fat, Uniqlo age 13 trousers (particularly the tapered leg ones) are really good, comfy and a bit roomier round the waste.
It’s been a real challenge trying to find clothing to fit kids who aren’t in adults sizing but are too big for kids clothes but these are really good. Pricy but they do often have good sales.