Who gives a ****? I attended a state grammar-school, and a public-schooler I befriended (whom I'd mistaken myself for state-educated) guessed that I'd graduated from Eton.
Anyone that would allow their character to be defined by something so arbitrary and extraneous as social and economic status, regardless of background, is probably precisely the sort of vapid, snobbish, stereotypical cretin whom you should be taking absolute pains to avoid while at university. Alternatively, if you belong to such a coterie yourself: 'old boys' don't simply disappear into the ether after you graduate into your much-vaunted I.B./Magic Circle traineeship (indeed they are, if anything, more prevalent), so you'd better bloody well get used to it.