not the case for my ds1 he is a real skinny and don't have aproblem. he was 8 yesterday and i buy him age 7 and they fit fine!
(he is 8 but now weighs the same as his 3 year old brother! and has only recently caught up with him)
I found Adams polo shirts great!! Paid £7.99 each for a couple of schools "logo" shirts, they didn't tumble and the went really bobbly. The Adams ones were worn over and over again, kept their shape and didn't bobble at all...
..the trousers on the other hand...DS is a skinny little thing and we struggles to get him any that were long enough in the leg but didn't fall down! He wore Adams trousers for ages though I must admit, they did bobble but at least they fitted.
Another vote for M&S, although the Woolies ones weren't too bad either. ds is always too skinny for his trousers wherever we buy them from! Our school polo shirts are fine after two years of wear, but they come from the PTA. Never iron anything!
I'd vote for Adams. Shirts tumble great, trousers are O.K. too, although I find you don't need to tumble as they dry really quickly.
We have 4 pairs, I wash them and hang them propryly folded on a Lakeland radiator airer overnight, they're dry by morning.