Pupils from deprived backgrounds are being conned into thinking they can advance in life by a system that hands out "worthless" qualifications, Harrow school's headteacher said today.

State schools risk producing students like "those girls in the first round of the X Factor" who tell the judges they want to be the next Britney Spears but cannot sing a note, Barnaby Lenon said.

Bright children from poor backgrounds are being short-changed by those who lead them to believe that "high grades in soft subjects" and going to "any old university to read any subject" were the route to prosperity, he told a conference of leading private and state school headteachers.

Meanwhile, at independent schools, pupils were being encouraged to take the toughest subjects, such as sciences and modern languages, and many were doing qualifications seen as more rigorous than regular GCSEs and A-levels, such as International GCSEs and the International Baccalaureate.

"Let us not deceive our children, especially children from poorer homes, with worthless qualifications, so they become like the citizens of Weimar Germany or Robert Mugabe's Zimbabwe, carrying their certificates around in a ­wheelbarrow," Lenon said.

Michael Gove, the shadow education secretary, backed Lenon. Media studies had seen a big increase in popularity in state schools, simply because it boosted their position in the league tables, he told the conference of the 100 Group discussing social mobility.

"More children who were eligible for free school meals sat GCSEs in media ­studies than in physics, chemistry and biology combined," Gove said.

The Tories are planning a return to more academically driven schooling, including setting by ability and traditional subject-based classes, if elected this year. At the moment, the only subjects students are required to take at GCSE are English and maths, after the requirement for them to study a ­language was dropped in 2004.

Earlier this week a report by CiLT, the national centre for languages, said ­language learning was in danger of­ becoming a "twilight" subject taken only by pupils prepared to stay on after school.

Last summer, just 41% of pupils from comprehensives took a language GCSE, compared with 81% of pupils in private schools. Last week research revealed that increasing numbers of independent schools are shunning GCSEs and A-levels to offer exams they believe are more academically testing, raising fears of a widening gulf between state and private schools.

Lenon said he believed that the UK's standard of education fell when CSE and O-level exams were abandoned in favour of GCSEs. "The road to social mobility is not a downhill stretch on an empty motorway, it is an agonisingly steep path up a ­mountain whose summit is never quite in view," he said.

A spokesman for the Department for Children, Schools and Families said: "These are pretty cheap and insulting comments. It's easy to make sweeping, rhetorical flourishes about so-called 'hard' and 'soft' subjects – but it is wrong to ignore the hard work of tens of thousands of teachers and pupils and misrepresent the state of education in this country."