Labour leader Sir Keir Starmer used Prime Minister’s Questions to call for an end to the "scandal" of tax breaks for private schools.
Private schools can claim charitable status so are eligible for tax relief.
Sir Keir pointed out Winchester College – the school based in Hampshire where Mr Sunak has attended – had rowing and rifle clubs, an extensive art collection and charged more than £45,000 a year in fees, but had received taxpayers’ funds.
“Why did he hand them nearly £6 million of taxpayers’ money this year in what he’s levelling-up secretary [Michael Gove] calls calls egregious state support?” Sir Keir asked.
Mr Sunak responded: “I’m pleased he wants to talk about schools because we recently announced billions more in funding for schools. We’re helping millions of the most disadvantaged children with their lost learning … but during Covid, he wanted to keep schools closed. We shouldn’t be surprised because I listen to parents and he listens to his union paymasters.”
The Prime Minister added: "Whenever he attacks me about where I went to school, he is attacking the hard-working aspiration of millions of people in this country, he's attacking people like my parents.
"This is a country that believes in opportunity not resentment. He doesn't understand that and that's why he's not fit to lead."
Sir Keir said it was “laughable” the Prime Minister thought the better route to education was tax breaks for schools.
”Trickle down education is nonsense,” the Labour leader said. “His education minister asks how much better it would be if the Tories get rid of handouts.”
Sir Keir separately told the PM that Labour will lend the Government the votes it needed to pass the Levelling-up and Regeneration Bill with mandatory housing targets.
His comments come days after the UK Government was forced to pull a vote on plans for mandatory, centrally-set targets to build 300,000 homes a year, after around 50 Tory MPs signed an amendment that would have scrapped the targets
Earlier, Mr Sunak was quizzed over Scottish independence in the wake of last week’s Supreme Court ruling that Holyrood did not have the powers to legislate for indyref2.
Asked by SNP MP for Edinburgh East, Tommy Sheppard, on whether he would clear the path for legislation for another Scottish independence referendum, Mr Sunak responded: "We did have that conversation not too many years ago. It was described as a once-in-a-generation referendum and we discussed this last week.
"I think what the people of Scotland want is for us to be working constructively together, to focus on their priorities. That’s indeed what we’re doing in his own area, investing hundreds of millions of pounds in a new growth deal and ensuring that with a new concert hall, we can enshrine Edinburgh’s reputation as a city of culture.