Just come across this, as they say, discussion point:

With the Conservative victory in the local elections, and Boris’s election to the London Mayoralty, the left are looking to try the ‘Tory toffs’ card for all it’s worth. To be fair, they do seem to be running out of alternatives. John Harris, who also wrote a marvellously whiny post-election article, has written about the apparent lock-down of the Conservatives by public schoolboys. It’s hampered a bit by Harris’s inability to entertain the possibility that one of the reasons that the proportions of public school entrants to Oxbridge may be because the public schools really do produce better students than the state sector, ...

Partly that, I daresay.  Plus maybe the better students tend to go to public schools in the first place ... ?  I think the Guardian piece linked to in the quote contains the biggest clue, with the word “networked” in its title.