Funded by the Nuffield Foundation, the study also concluded that special school teachers are less likely to have qualified teacher status (QTS).

“This may suggest special schools are more willing to use a wider pool of candidates when recruiting teachers,” it said.

The findings come as the Children’s Wellbeing and Schools Bill requires teachers in academies to have, or be in the process of achieving, QTS.

The NFER has called for work to be done to understand why 10 per cent of teachers in special schools do not have QTS, compared with the national average of 3 per cent.

Margaret Mulholland, Send and inclusion specialist at the Association of School and College Leaders, said: “Special schools may recruit teachers with strong backgrounds in special educational needs therapies, but who do not have QTS.

“This is one of the reasons that the government has to be careful about how it implements planned legislation over requiring all teachers to have QTS so it does not worsen existing pressures.”

Rob Williams, senior policy adviser at school leaders’ union NAHT, said: “The unpalatable truth is that in some areas, teaching assistants can earn more working in a cafe or supermarket, and we need the government to do more to improve their pay.”

The DfE was contacted for comment.