A shift towards traditional subjects at GCSE risks "demotivating and alienating" thousands of teenagers, a union leader has warned.
Dr Mary Bousted suggested that the introduction of the Government's flagship English Baccalaureate (EBacc) will restrict pupils' GCSE choices, leaving many without the crucial skills they need for the future.
Her warning comes as teenagers across England, Wales and Northern Ireland wake up to their GCSE results.
To gain the EBacc pupils must score at least a C grade at GCSE in English, maths, science, a foreign language and history or geography. While the EBacc is not compulsory, it has been widely predicted that many secondary schools will begin to steer pupils towards these subjects.
The EBacc was included in league tables for the first time earlier this year, with just one in six teenagers in England (15.6%) achieving it.
Dr Bousted, general secretary of the Association of Teachers and Lecturers, said she expects some "great results", but added: "If the Government has its way, this year's 16-year-olds will be the last to have had a real choice of subjects and qualifications.
"Education Secretary Michael Gove's English Baccalaureate is likely to restrict the range of subjects taught to GCSE.
"This risks demotivating and alienating the thousands of young people who struggle with academic subjects and would be better suited to taking a wider variety of subjects to give them the skills for a range of careers."
A DfE spokesman said: "The EBacc is not compulsory and is only one measure of success - pupils should study what is right for them.
"It makes up just five subjects, three of which are compulsory anyway. There is plenty of time left for pupils to study other subjects."