Youth unemployment is being fuelled by teenagers leaving schools without GCSEs in English and maths, research suggests.
A new study raises concerns that half of young people in England's cities are not getting good enough grades to secure them a job.
The report, by Centre for Cities, suggests there is a strong link between achievement in English and maths and youth unemployment, with a gap between cities with strong economies and those with weaker ones.
The findings show that in 1996/97, schools in cities with good economies had the largest numbers of pupils gaining at least five C grades at GCSE in any subject, while struggling cities had the lowest.
By 2009/10 this gap had disappeared.
But a gap remained in the numbers of pupils gaining five good GCSEs including English and maths.
The report raises concerns that over the last few years, schools have been encouraging pupils to study for qualifications that are seen as easier to achieve to boost their position in league tables.
It concludes: "Incentives in the education system mean that pupils in struggling cities in particular are not being equipped with the skills required in the changing labour market.
"This is likely to reduce the employment opportunities of these people and compound the skills issues that these cities face.
"Incentives need to be realigned to encourage both maths and English attainment and educational improvement across all grades at GCSE."