As many as 50 MPs who went to grammar schools themselves are likely to oppose rumoured Government plans to roll out selective education more widely.
Some 44 Labour MPs, Lib Dems, SNP members, as well as some Tories are set to number among them.
Despite their ability being recognised – and rewarded – by the state in their schooling, members of most non-Tory parties are likely to try to stop the same advantage being extended to others.
The issue is a fraught one – with many MPs taking care not to make their true feelings known on the matter for fear of contradicting Government policy or sparking a row.
Indeed, some MPs even refuse to make public where they went to school, depriving the public of the opportunity to fully judge their views.
The figures have been produced by Heat Street in light of reports this weekend that Theresa May’s government could back the establishment of new selective schools.
Heat Street‘s estimates for the levels of opposition are based on a large-scale study of MPs carried out by the Sutton Trust at the beginning of this parliament.
It found that 19 per cent of MPs – around 123 – went to selective state schools.
Around 60 are Conservatives, 44 are Labour, 2 are SNP and 2 are Lib Dem.
Almost half of MPs from other parties were selectively educated – likely due to members from Northern Ireland, where selection is still widespread.
The data had to be anonymised after some MPs only agreed to share their educational background if their names were kept secret.
Even if every grammar school-educated Tory backed the expansion, that would still leave around 50 MPs from mainstream opposition parties likely to oppose the measures in accordance with the party line.
The figure has been in decline for some time since an ever-increasing proportion of MPs were educated after the mass roll-out of comprehensive schools. In the 2010-15 Parliament the figure was 24%.
Until briefings over the weekend to the Sunday Telegraph, the government was opposed to new grammar schools, though it did let one location open an “annexe”, seen as a back-door way to expand selection.
This position would have obliged front-bench MPs to keep quiet on new grammar schools even if they fervently supported them.
Instead the job was left to vocal Tory backbenchers like Graham Brady, who quit the front bench in 2007 so he could keep campaigning on the issue.
The campaign group Conservative Voice has also spent years campaigning for an expansion, and recently estimated it could count on support from 100 MPs.
Speaking to Heat Street, Conservative Voice founder Don Porter said he is still “very confident” in the figure and had received warm reactions in private from many MPs in light of the reports.
He said his organisation will start campaigning more widely once Parliament reconvenes next month.
MPs’ educational backgrounds has long been a major feature of political debate – with Etonians like David Cameron and Boris Johnson being constantly reminded of their privilege.
Privately-educated Jeremy Corbyn largely avoids any such scrutiny – though he has arguably proved his commitment to that cause beyond reasonable doubt.
The leader of the opposition divorced his second wife in 1997 after she insisted on sending one of his sons to a selective school in outer London rather than his local Islington comprehensive.
Other MPs to endure public scrutiny include Michael Gove and David Cameron, who both sent children to the well-to-do Grey Coat Hospital school – technically a comprehensive, but one widely seen as offering a better class of schooling.
Diane Abbott famously sent her son to a private school, criticised Harriet Harman for doing the same, and then claimed special dispensation because of her West Indian background.
Meanwhile, comprehensively-educated politicians, particularly from the Left, are unlikely to let you forget it – with vocal examples including leadership contenders Angela Eagle and Owen Smith.