Changes to the way sixth forms and further education colleges are funded have left grammar schools struggling to cope, the government has been told.
Kent Conservative MPs Damian Green and Gareth Johnson said the changes had adversely affected grammars disproportionately to other schools.
Mr Green said one school in Ashford, Highworth Grammar, had been forced to cut the number of A-level subjects.
Schools minister Nick Gibb said difficult decisions had had to be made.
Paid per pupil
The MPs were speaking at a debate on grammar school funding.
Sir Edward Leigh, Conservative MP for Gainsborough in Lincolnshire, said changes introduced in 2013 - schools are now paid per pupil rather than by the number of qualifications - had resulted in "unintended consequences".
Mr Green said Highworth Grammar was running A-level classes for German with a class size of 11 and for French and Spanish with class sizes of seven.
"With the financial squeeze that will no longer become viable and that would be appalling," he said.
"Already in this school the A-levels offered have gone down from 40 to 32.
"This one perversity in the system is actually damaging the life chances of some of our most academic children at some of our best schools," he said.
John Glen, Conservative MP for Salisbury and South Wiltshire, said there were concerns that the 164 grammar schools in England were being put at risk.
Mr Gibb said education reforms had "massively improved" the life chances of millions of children.
But he acknowledged concerns that savings in education had fallen disproportionately on grammar schools and successful comprehensive schools with large academic sixth forms.
He said the aim was to make sure that as many young people as possible left school with the right knowledge and skills to be able to succeed in adult life.