League tables are a key driver of England's education system
Some independent schools are preventing children from taking exams unless they are confident they will achieve top grades, say leading head teachers.
The move is blamed on the pressure of league tables and the need to maintain a high ranking and status.
The Boarding Schools' Association (BSA) chairman Geoffrey Boult says state schools face similar pressure.
The government says league tables are here to stay and parents must be kept informed of a school's performance.
Mr Boult, who is head master of Giggleswick School in North Yorkshire, will use his address to the annual BSA conference for head teachers as a platform to highlight what he sees as the pitfalls of an education system driven by league tables.
Speaking to the BBC News website ahead of the conference he said both the independent and state sectors had pandered to the demands of the tables.
The league tables put massive pressure on headmasters to do bad things
Martin Stephen, high master, St Paul's School, Barnes
He claimed schools in both sectors were discouraging pupils from taking more difficult subjects at GCSE and A-level, which had led to a decline in science and languages.
Instead they steered pupils towards subjects where it was considered easier to gain the top grades and in some cases prevented them from taking exams if they thought they would struggle to reach the top.
Mr Boult said: "To support our children in the state sector we should fight against league tables.
"Science and languages are disappearing from state schools because they are too hard.
"League tables are corrosive."
Martin Stephen, the high master of St Paul's School at Barnes, south-west London, which takes boarders, will make similar claims at the conference.
He is a former chairman of the Headmasters' and Headmistresses' Conference (HMC), which represents the heads of some 250 leading independent schools in the United Kingdom and the Republic of Ireland.
His personal view is that some independent schools are preventing less able pupils from taking exams because they worry about rankings.
He said: "The league tables put massive pressure on headmasters to do bad things.
"There is tremendous pressure on all schools not to let pupils into the sixth form if they're not going to make the grade.
"League tables brand a failing school on the forehead and make it very hard for a school to get out of failure."
Dr Stephen told BBC Radio 4's Today programme: "Nobody in the world, apart from those in Whitehall, believes for instance that A-level general studies counts as a full A-level, yet the January league tables religiously, year after year, keep saying that it does.
"These league tables are a lie and I am a school master and I tell pupils not to tell lies and I think I should tell the government not to tell lies."
St Paul's and Eton College have said they will not submit their results for the separate tables compiled each August by the Independent Schools Council.
Parents have a clear right to know how well their school is doing - and publication of results is here to stay
Mr Boult said boarding schools were challenging the "tyranny" of league tables and continuing to concentrate on an inclusive, "rounded" education.
This included teaching children how to lose and how to fail, not just how to succeed.
He said: "Boarding schools do this all the time, through our numerous competitions in sport, music, drama, chess, debating, et cetera.
"We have daily winners and losers; it is part of our life."
The Department for Children, Schools and Families (DCSF) said league tables were essential.
A DCSF spokeswoman said: "Parents have a clear right to know how well their school is doing and publication of results is here to stay - though we do not, and never have, published ranked league tables.
"It is wrong to say schools are opting for easy subjects - English, maths and science are all compulsory at GCSE."
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.