An adviser to the PM has defended an interview in which he said Eton's "ethos" of public service was why so many former pupils were in top positions in government.
Tory MP and Old Etonian Jesse Norman told the Times: "Other schools don't have the same commitment".
Mr Norman clarified his comments on Twitter later, saying he was not attacking other schools.
He was appointed to David Cameron's parliamentary board this week.
"Other schools don't have the same commitment to public service. They do other things," he told the newspaper.
'Defending not attacking'
"It's one of the few schools where the pupils really do run vast chunks of the school themselves. So they don't defer in quite the same way, they do think there's the possibility of making change through their own actions.
"Of course, they are highly privileged - it would be absurd to deny that - but the whole point of what Michael Gove [education secretary] is trying to do is to recover that independent school ethos within the state system, so that people from whatever walk of life can feel that they can take a proper part to the maximum," Mr Norman said.
The prime minister - who is Britain's 19th prime minister to have been educated at the Berkshire school - has faced criticism over the number of fellow Etonians in top government positions.
They include chief of staff Ed Llewellyn, Cabinet Office minister Oliver Letwin, chief whip Sir George Young and new policy unit head Jo Johnson - who is brother of London Mayor Boris Johnson, another former pupil.
Mr Norman said the school's "old-fashioned" principles had helped its students succeed.
"Things like rhetoric and poetry and public speaking and performance are incredibly important to young people succeeding in life," said the MP for Hereford and South Herefordshire.
Later on Twitter, Mr Norman said his comments were "defending one institution, not attacking others".
He also suggested he had been referring to public rather than state schools, and had meant that other public schools "don't always" have the same commitment to public service".
In his interview with the Times, he went on: "I didn't know any of the people at the top of government when I was at school. I did know Boris.
"He was a couple of years below me. But then everyone knew Boris. He was a rather distinctive figure. Jo is much younger. I knew Cameron's brother slightly, but he wasn't in my year."
Mr Norman said it was "tragic" class still appeared to be important in Britain.
"I wish we could find some way of creating a society which was freer in its own mind about that," he said.
"The problem is when you have a preoccupation with class, you get people believing that they can't succeed.
"I've no doubt that the big universities are dying for more people to apply from less privileged backgrounds, but they aren't getting them. That's one of the problems."