“Unsustainable” pressure on school staff could put the government’s education recovery plans at risk, a school leaders’ union has warned.

Paul Whiteman, general secretary of the NAHT school leaders’ union, believes an “exodus” of headteachers could take place post-Covid after an “exhausting” and “stressful” year for school staff.

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He made his comments after, in a survey by the union, nearly half (46 per cent) of school leaders said they had 31 per cent or more of their normal roll attending class in person before February half-term.

More than one in eight (13 per cent) said they had 41-50 per cent of pupils come into school amid the lockdown.

The overwhelming majority (91 per cent) of school leaders said demand for places - among children of key workers and vulnerable pupils - has increased since the beginning of the current lockdown.

Covid: School leaders ‘are on their knees’

Some 64 per cent of school leaders said they have worked at least six additional hours per week on average since the beginning of this term as a result of the coronavirus pandemic.

Nearly two in five (38 per cent) said they have worked an average of 51-60 hours a week since the start of term, according to the survey of more than 3,000 school leaders across England in February.

Mr Whiteman said: “These figures prove once and for all that schools are not and have never been closed.

“Teachers and school leaders have, in fact, been working harder than ever to juggle the demands of remote teaching for pupils at home, while also caring for those vulnerable and key worker children in school.

“The worry is that the workload and pressure on school staff at the moment is simply unsustainable - and could threaten the education recovery to come.”

The latest government figures suggest that more than one in four (27 per cent) of primary school pupils in England were taught on-site last week.

Overall, 18 per cent of state school pupils were in class last week, up from 16 per cent before half-term, according to the Department for Education (DfE) statistics.

All pupils in England will return to class from Monday after months of remote learning.

Mr Whiteman added: “This is potentially the most important moment of the pandemic for children and young people - the point at which we finally see the light at the end of the tunnel and prepare to throw everything we have into providing the best conditions possible for pupil recovery.

“We need teachers and school staff refreshed and ready to be the very best and brightest they can be for the pupils relying on them.

“Instead, many school leaders are considering leaving the profession prematurely, once they have guided their schools through this crisis.

“The top three words our members have used to describe their experience of the past year are ‘challenging’, ‘exhausting’ and ‘stressful’. There is a real concern that we will see a ‘post-Covid exodus’ of school leaders.”

Last week, Boris Johnson announced an extra £400 million of funding - on top of the £300 million pledged in January - to help pupils make up lost learning time following closures.

As part of the recovery package, secondary schools have been asked to deliver some summer teaching, and tutoring schemes will be expanded.

The government considered a variety of options as part of the catch-up plans - such as extended school days and shorter summer holidays - but they were not included as part of the immediate proposals to recover lost learning.

Mr Whiteman warned: “It is vital that we take a long-term view of recovery and don’t rush into quick fixes that could do more harm than good. Both children and educators need time to heal and recover - time to get back to what they know best before more pressure is piled onto them.

“Recovery won’t happen in a single summer. The biggest driver of educational success for children is great teaching by great teachers. The best thing the government can do now is to value and invest in all teaching staff.”

Sinead Mc Brearty, chief executive of charity Education Support, said headteachers “are clearly on their knees”.

She added: “Teacher and pupil wellbeing is inextricably linked and no one can do their best if mentally and emotionally depleted.

“The profession needs to be well-equipped if it is to support our children and young people to successfully recover from the impact of this global crisis.”