Jeremy Corbyn delivered one of his strongest ever performances at Prime Minister's Questions this afternoon (14 September), as he grilled Theresa May over her plans to allow state schools across England to select on educational ability.

The Labour leader faced criticism for failing to raise the issue during last week's House of Commons exchange, but Corbyn devoted all six of his questions to the controversial proposal this time around.

"In Kent, which has a grammar school system, 27% of the pupils on free school meals get five good GCSEs, compared with 45% in London," the left-winger said.

"We are all for spreading good practice, but why does the prime minister want to expand a system that can only let children down?"

May hit back by urging Corbyn to "stop casting his mind back to the 1950s", a reference to Corbyn's grammar schools days in Shropshire.

"What we will be doing is ensuring that we will be able to provide good school places for the one and a quarter million children who are in schools which are failing, inadequate or need improvement," the Conservative premier added.

"Those children, and the parents of those children know, they are not getting the education that is right for them and the opportunities that they need."

But Corbyn continued to press May on the matter, even providing a quick counter to the prime minister's claim that Labour want to pull the ladder of opportunity away from youngsters.

"It's not about pulling up ladders, it's about providing a ladder for every child," Corbyn said.

May, who faces serious opposition from backbenches over the grammar schools plan – such as former Education Secretary Nicky Morgan – attempted to steer the debate towards the positive employment figures released by the Office for National Statistics (ONS) this morning.

But Corbyn was able to bring the conversation back to topic. "Of course I welcome anyone who's been able to get a job, I welcome those people who have been able to get jobs and keep themselves and their families together," he said.

"The problem is that there are now almost one million of them on zero-hours contracts, who do not know what they are going to be paid from one week or another."

The Labour leader added: "Isn't this all proof that the Conservative Party's green paper addresses none of the actual crises facing our schools system?

"A reals-term cut in the schools budget, half a million pupils in super-sized classes, a crisis in teacher recruitment and teacher retention...isn't this the case of a government heading backwards to a failed segregation for the few and second-class schooling for the many?"

The exchange came just two days after former Prime Minister David Cameron resigned as the Conservative MP for Witney, triggering a by-election for the Oxfordshire seat.

He argued in 2007 that rejecting new grammar schools would show the Conservatives were now "an aspiring party of government", rather than a "right-wing debating society".