Grammar schools have been accused of failing to challenge brighter pupils and not setting targets high enough at GCSE levels.
A report released on Thursday also showed considerable regional variance in the performance of grammar schools.
It claims the current benchmark of five A*-Cs, including English and maths, is too low and should be set at five As or A*s for brighter students.
The report's author, Professor David Jesson, of the University of York, advocates increasing the bar and potentially extending this to other schools as a way of assessing their impact on the most able youngsters.
"Grammar schools should expect to achieve high levels of performance for their pupils and most do," Prof Jesson said.
"There are, however, substantial differences between grammar schools' outcomes which tend to go unnoticed in the standard performance tables.
"If we are genuinely committed to the idea of excellence for all, we need a new way of measuring the performance of these schools and making sure that every pupil reaches their full potential."
In his Great Expectations report, he observes "coasting" or under-performance could have gone undetected. He also suggests standards could be pushed up across the board.
While changes in expectations could raise the bar "substantially" in some schools, he argues many would be offered a "fresh challenge to match the best that others have shown to be possible".
"In this way, grammar schools can play a full part in the relentless search for excellence which is the focus of much government policy," he writes.
"The beneficiaries will be their pupils and the nation as a whole if these pupils are challenged, encouraged and inspired to achieve the very best that others like them have shown to be possible."
His report forms part of a debate on school performance measures launched by The Schools Network, an independent, not-for-profit organisation which represents more than 5,000 schools and academies.
Jesson, associate director of The Schools Network, based his conclusions on a fresh analysis of grammar school performance.
Sue Williamson, the organisation's chief executive, said: "Schools are always looking to raise the bar and to push all of their pupils further.
"Our members recognise that every pupil is different and that every child has talent which schools must strive to make the most of."
Hailing the "groundbreaking" study, she added: "We look forward to the opportunity of developing this research further and ensuring that every young person is given the chance to achieve their full potential."
A Department for Education spokesman said: "No school can ever afford to rest on its laurels.
"We want to make sure that all schools are stretching their brightest pupils and that schools with very able intakes are helping students reach their full potential rather than allowing them to coast along.
"The tables now show expected and actual performance for low, middle and high-attaining pupils so that schools can be judged on whether they are improving all their students."
Grammar schools have long come under fire for the exam system which divides pupils at the age of 10 or 11. Critics claim the 11 plus separates children according to intellectual ability at too young an age and has a detrimental impact on their self-confidence.
A controversial plan in Sevenoaks, Kent, to build an annex to an existing grammar school was recently approved by the council, despite widespread opposition.