School trousers for man child?

[justsaythanks]

Has anyone got a favourite source of trousers for year 11, medium man sized boy? He rips the thinning Next ones at the pocket and Asda ones go in holes. I'm hankering after the reinforced knees and coated fabric of school trousers but he's too big !
Where do I get ones that won't cost me £100 for 3 pairs ?

We get ours from Matalan mens department, they aren't too expensive and seem pretty robust.

Nothing wrong with Primark trousers, especially as he could easily grow a lot more over the next 2-4 years.

They're good enough for adults, they're good enough for teenagers.

Do you know I didn't think of either of these.
Are they both in the men's bit?