Government urged to demonstrate how grammar schools would 'close attainment gap'
Pupils should not be admitted to grammar school simply on the basis of passing a selection test, MPs have warned.
Ministers have not yet shown how an admission system for selective schools could be set up that could not be "gamed" by families who can afford to pay for tutors, according to a report by the education select committee.
The cross-party group of MPs also said the Government must demonstrate that creating a new wave of grammars will help close the achievement gap between rich and poor children.
Plans to expand selective state school education were unveiled by Prime Minister Theresa May last autumn.
Children are awarded places to grammar schools based on academic ability - typically through their performance on a test such as the 11 plus.
In a new report, the select committee says it was told by Schools Minister Nick Gibb that creating a tutor-proof entrance test for grammar schools is a "holy grail".
If this is the case, the MPs conclude then selection tests "should not be the only basis on which admissions to grammar schools are based".
"The Government has yet to demonstrate how an admissions system could be designed in a manner which would be immune to gaming, or being reduced to the ability to pay," the report says.
It also concludes: "The Government must demonstrate how the creation of new grammar schools will help close the attainment gap within the wider school system, not just for individual pupils."
Committee chair Neil Carmichael said: "The Government has yet to prove the case for opening a new wave of grammar schools.
"The Prime Minister rightly talks of making Britain a great meritocracy.
"If the Government wants to push ahead with new grammar schools it must demonstrate how this aids social mobility and improves educational outcomes for all, most especially those from disadvantaged backgrounds.
"The focus on opening new grammar schools is, in my view, an unnecessary distraction from the need to ensure all our young people are equipped with the skills to compete in the modern workplace.
"A broadly skilled workforce is crucial to the future success of the UK economy.
"If the Government is committed to increased specialisation in our education system then they should spell out how this meets the aims of the Industrial Strategy and the goal of an economy that works for all."
Mrs May has argued that grammars can help the life chances of poor pupils, and that the current system sees ''selection by stealth'' based on parents' wealth and ability to buy houses near the best schools.
But proposals have attracted criticism, including from high-profile figures such as former Ofsted chief Sir Michael Wilshaw and headteachers.
Opponents argue that expansion will lead to segregation and a two-tier education system.