Large numbers of pupils are being “failed” by tougher new GCSEs, according to a survey of secondary school leaders.

The research by the Association of School and College Leaders (ASCL) found that 80 per cent of school leaders thought that the intentional increased difficulty of the GCSEs had “detrimentally affected” lower-ability students.

New GCSEs: Schools battle to help ‘forgotten third’

Related: Analysis: Does GCSE maths let down the forgotten third?

News: GCSE maths not fit for purpose say 81% of teachers

“A large proportion of students are being failed by the new GCSEs. Not everyone is suited to them and, while they may be a good pathway for those students going onto A level or degree level, they are simply not fit for purpose for students who may thrive with a more vocational route,” one school leader said.

“These students are made to feel they are constantly failing no matter how hard they work because they struggle to retain the list of endless facts they need for their exams.”

The study, which surveyed 554 school leaders in England last month, also found that nearly 8 in 10 school leaders - 79 per cent - said the revised qualifications were causing higher levels of student stress.

One deputy headteacher said: “Lower-attaining students are completely demoralised by these new exams. We have an increasing number refusing to attempt mocks and actual exams. This has never happened before.”

An assistant headteacher said: “These have been designed without a thought for low prior attaining or SEN students. I cannot think of anything more dispiriting than going through school thinking every day: ‘I cannot do this’. But that is the reality for many students.”

The news comes after Tes revealed that more than 500 schools have signed up to a programme to support the “forgotten third” - pupils who fail to achieve grade 4s in English and maths - amid concerns about the new qualifications. 

Meanwhile a snap Tes poll found that 81 per cent of teachers think the revised curriculum in GCSE maths is “not fit for purpose”.

The ASCL survey also asked school leaders about the benefits of the reformed exams. The most commonly cited advantage was that the new qualifications prepare students better for the next stage of their education or careers, with 46 per cent of respondents saying this was an advantage.

One in five school leaders - 22 per cent - said the greater level of challenge was more fulfilling for students.

However, some respondents said the greater level of challenge benefited only the most able students, while more than a third of respondents - 35 per cent - said there were no benefits.

Geoff Barton, ASCL general secretary, said: “The government has seen increased rigour as an end in itself without fully considering what it wants the exam system to achieve for all students of all abilities.

“As a result, we now have a set of GCSEs which are extremely hard to access for students with lower prior attainment. This is incredibly stressful and demoralising for these young people.

“We need a system which allows every young person to finish their schooling with qualifications of which they can be proud.

“It is absolutely right that we aspire to the highest standards for all our young people but serving up a diet of exams which erodes the confidence of a large proportion of young people is surely not the way to achieve this objective.”