Official figures suggest rising numbers of secondary schools are under-performing.
New data shows one in eight of England's mainstream secondaries - 365 in total - fell below the government's minimum standards in 2017
This is up from 282 schools, just under one in 10 - the year before.
Schools fall below the government's performance threshold if pupils fail to make enough progress across eight subjects, with particular weight given to English and maths.
The Department for Education suggested that the rise in under-performing schools is because of technical changes to the points system used by government statisticians to calculate a school's performance.
Thursday's data, which covers every secondary in England, shows that London has the lowest proportion of under-performing schools while the North East had the highest.
For the first time this year, the data includes English and maths GCSE results awarded under the new 9-1 grading system.
The figures also show that the attainment gap between rich and poor pupils has narrowed by 3.2% since 2016.
Schools Minister Nick Gibb said: "The attainment gap between the most disadvantaged pupils and their peers has narrowed by 10 per cent since 2011, and more disadvantaged pupils are studying the core academic subjects, ensuring they have the knowledge and skills they need to make the most of their lives."
Geoff Barton, general secretary of the Association of School and College Leaders said that the new grading system for English and maths has complicated the way in which school performance measures are calculated.
"Our message to the DfE, trust boards, governors and inspectors is to avoid leaping to judgement on the basis of these performance tables," he said.
"They only tell us a limited amount about the true quality of a school."
See how local schools performed in Friday's Wigan Post