Pupils in disadvantaged areas are being denied the chance to study science and foreign languages because they are considered too difficult, research suggests.
A new study claims that students are missing out on a wide curriculum because schools are more worried about their standing in league tables.
The research, conducted by the Open Public Services Network (OPSN) at the RSA thinktank showed that in six of the poorest areas in the country, more than a third of schools did not offer any students the opportunity to study triple science.
The study, which analysed GCSE results from 2013, highlighted North East Lincolnshire as the one of the worst areas, where half of secondaries were not offering triple science.
The others were Medway (35.3 per cent), Newcastle upon Tyne (36.4 per cent), Slough (36.4 per cent), Kingston-Upon-Hull (38.5 per cent) and Knowsley (42.9 per cent).
In modern foreign languages, children in London's Kensington and Chelsea, and Kingston-upon-Thames are significantly more likely to be entered for a GCSE in the subject than pupils in Middlesbrough, researchers said.
In total, just 24.4 per cent of teenagers in Middlesbrough were entered for a language GCSE in 2013. Other areas with low entries for languages include Barnsley (27 per cent of pupils) and Sandwell (28.3 per cent).
The areas with the highest proportions of pupils studying foreign languages are concentrated in London. Top is Kingston-upon-Thames at 69 per cent, followed by Kensington and Chelsea (67.6 per cent) and Hammersmith and Fulham (67.1 per cent).
OPSN chair Roger Taylor said that the data shows that children's educational opportunities are defined by where they live.
"They show that in some parts of Britain, opportunities are restricted because all the schools within a neighbourhood have decided not to offer more challenging subjects," he said.
"We can see that the curriculum taught to children in poorer parts of Britain is significantly different to that taught in wealthier areas. This would be of little concern if these differences reflected the needs and choices of pupils and families.
"Our worry is that instead they reflect decisions made by schools and are based on calculations as to how schools can appear better on league tables by encouraging children to avoid taking on more challenging subjects. The evidence suggests that in areas where most children are expected to do less well in exams, the educational opportunities for all children are being restricted."
Charlotte Alldritt, RSA director of public services, said that denying young people access to subjects like triple science "sends out a terrible message".
"It says that if you're young and poor, we expect you to fail," she said. "Rather than dumbing down our curriculum to achieve better grades, school leaders should be aiming to improve the standard of their teaching so that all children have the chance of going on to the academic or training courses they want and getting the best jobs available."
Government data published last year showed that hundreds of schools and colleges were failing to enter any pupils for science and maths A-levels – subjects seen as vital in part due to increasing demand for workers with backgrounds in these subjects.
The statistics also showed that the likelihood of a teenager studying one of these key subjects varies depending on where they live, with youngsters in London, along with the East Midlands and South West, more likely to take them.