Pupils are being put in the "GCSE pressure cooker" and drilled for public examination from as early as Year 7, teachers have claimed.
Delegates at the ATL-section of the NEU teaching union conference said that children were being fed GCSE questions "day in, day out", with some driven to tears because they felt they hadn't made enough progress.
Huw Tindall-Jones, a teacher from Devon, said that schools were forced to move to a four-year key stage 4, because of the pressure to do well in exams and cover a large amount of GCSE course content.
"This means that in some schools, Year 8 pupils will start their GCSE curriculums. These students are going to be 12 or 13 years old. They will be in the GCSE pressure cooker for four years and this is wrong.”
However, Chris Daye, a teacher from Solihull, said that in her school the maths department effectively operated a five year KS4, with students being drilled for GCSEs from Year 7.
"I actually realised that as a maths department, we’re actually running a five-year GCSE course," she said. "We’re actually grading each child based on the GCSE grades.
"I see Year 8 girls crying because they haven’t moved up half a grade on the next assessment test."
She added: "We do not give them the fun parts, we do not enrich the maths curriculum, we are just literally giving them GCSE exam questions day in, day out.
"This has to stop. We have to be able to teach KS3 children as the children they are – not the young adults in Year 10 and 11."
Mr Tindall-Jones said that a longer KS4 curriculum could damage pupils' well being. "Younger students will be more susceptible and at risk of deteriorating their own mental health,” he said.
The conference passed a motion instructing the union's executive to investigate the impact of a four year KS4 on the wellbeing of staff and students and GCSE results.