The education system is in danger of "deceiving" children from underprivileged backgrounds by handing out high grades in "soft" subjects, the headteacher of Harrow public school has warned.
Barnaby Lenon said subjects such as media studies have proved "extremely popular and successful" in state schools because they are easier to get good results in.
Pressure to achieve a good league table position, along with a lack of teachers in so-called "difficult" subjects such as science and languages, has fuelled the trend, he said.
The answer to a Parliamentary question last summer revealed that entries for A-level media studies more than quadrupled in state comprehensives between 1997 and 2008 from 2,821 to 12,661.
The number of pupils taking physics fell from 12,126 to 10,118, although it recovered from a low point of 9,916 in 2005.
By choosing "soft" subjects, able pupils from poor backgrounds are being denied access to the top universities and the subsequent social mobility that offers, Mr Lenon warned.
"We are in danger of deceiving pupils from poor homes with high grades in soft subjects," he said.
"The route to social mobility is not an easy one, it is a steep path up a mountain whose summit isn't always in view.
"Let's not encourage pupils from the poorest homes to take qualifications that don't mean much. To be a doctor, you need an A-grade in chemistry and maths and one other science."
Independent schools better recognise the importance of traditional subjects such as science, maths and languages to gaining top university places, he said.
Last year at Harrow, which charges annual boarding fees of #163;28,545, 65 out of 80 boys taking A-level maths scored A grades, and 53 per cent of GCSE grades awarded in all subjects were at A*.
Mr Lenon's comments come in the week that the Government launched its response to the Panel on Fair Access to the Professions' report on improving social mobility.
Mary Bousted, general secretary of the Association of Teachers and Lecturers, hit back at Mr Lenon for "the assumption that independent schools offer a 'proper' curriculum and state schools don't".
"Their own range of subjects is not necessarily suitable for the wide range of people they educate," she said. "Media studies has always been the bogeyman, but the idea that it is a soft subject is ridiculous.
"Pupils should of course get good careers advice on which subjects to do, but the brightest children from the poorest families aren't failing because of their choice of subjects, but because their lives are blighted by poverty and stress."
Mr Lenon spoke to The TES prior to addressing a gathering of 100 leading independent and state school heads at the 100 Group Conference in east London today.
The event, which tackles the theme of social mobility, was due to be attended by high profile figures, including Tony Little, the headmaster of Eton, and Michael Gove, the shadow schools secretary.