1 or 2 recent threads elluded to the claim you can tell good schools from bad simply by the standard of their uniform. So a school that insisted (successfully) on a traditional uniform like blazers, ties, pleated skirts, tucked in shirts etc. were generally better than a school of kids dressed like ragamuffins. Though in some ways a sloppy uniform is worse than no uniform but tidy jeans, T shirt etc. so depends how you definie smart.
Certainly in Glasgow all the private schools have this kind of smart uniform and the top non private (not council run either but hey) also does (and though not private they have huge waiting lists so can probably enforce it easily). Poorer schools tend to have very scruffy kids miandering about its grounds and outside. (anyone playing the poverty card, there are clothing grants for such families)
There are exceptions to every rule so please don't tell me that. In general though.