State schools are holding back some of the country's brightest pupils from reaching their full potential, the chief inspector of schools has warned.
Sir Michael Wilshaw has raised concerns that children who leave primary school with top grades are left to coast by some teachers when they reach secondary school.
He has ordered a "rapid response survey" to see how state schools teach the most able children, Sir Michael told The Sunday Telegraph.
It comes after new figures revealed last week that hundreds of schools failed to produce at least one pupil with good enough grades in academics subjects to enter elite universities.
The former head of Mossbourne Academy, in Hackney, east London, believes all students should be pushed as hard as those at independent and selective schools.
He said: "I am concerned that our most able pupils are not doing as well as they should be.
"Are schools pushing them in the way they should be pushed and are pushed in the independent sector and in the selective system?
"I am as concerned as the next person on the issue of social mobility.
"Are our children and our children from the poorest backgrounds who are naturally bright doing as well as they should?"
He urged that the gap in admissions to Cambridge and Oxford universities between private and state schools be addressed.
Some schools were too focused on gaining C grades, because it is this measure which counts in league tables, when pupils had the capacity to achieve a A* or A grades, he he added.
The report, which will take a representative sample of more than 50 secondary schools, will be published later this year.