As schools reopen to certain year groups today, the number of school staff is expected to be down by a quarter as more than a fifth of teachers are able to work only at home, a survey finds.

At the same time, headteachers are predicting that almost half of families will be keeping their children at home, according to the survey by the National Foundation for Educational Research (NFER).

NFER chief executive Carole Willis said there would be differing and changeable levels of staffing and parental choices and that there would be large variations between different types of schools across the country.

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She said: ”Each [school will be] experiencing their own challenges in opening to more pupils. Government guidance needs to be tailored and responsive, allowing flexibility for school leaders to use their professional judgement.”

The national survey of 1,233 senior leaders in publicly-funded, mainstream primary and secondary schools in England was carried out between 7 and 17 May.

It found school leaders were operating with 75 per cent of their normal teaching capacity, while 29 per cent of teachers are able to work only at home. The NEFR says reasons are likely to include commitments to child care and the need for staff to self-isolate (although this is not in the report).

Senior leaders said they would need extra staff both for pupils on site as well as for distance learning and to cover for absent staff -and that this would require additional funding. Lack of staff would also affect the quality of teaching, they said.

Meanwhile, school leaders with the highest proportion of free school meal (FSM) pupils estimated that 50 per cent of families would keep children at home - compared with an average estimate of 42 per cent from leaders with the lowest proportion of FSM pupils. The NFER says this raises concerns that pupils in most need of access to education will be least likely to receive it.

The survey also found that 65 per cent of primary and 73 per cent of secondary leaders think it would be feasible to operate a rota with different year groups or classes in school on different days.

Josh Hillman, director of education at Nuffield Foundation, which funded the research, said: “With more pupils returning to school from today, school leaders are particularly concerned about the challenge of running parallel school and home-based learning programmes.

“This challenge is compounded by their expectations that high proportions of families will choose to keep their children at home, particularly those from disadvantaged backgrounds.

The DfE said it would continue to work with schools “to identify and help resolve any practical issues”.

Education secretary Gavin Williamson said: “Throughout the Covid-19 pandemic, our decisions have been based on the best scientific and medical advice, with the welfare of children and staff at the heart of all considerations.

“The prime minister has announced that the government’s five tests have been met and, based on all the evidence, we will now move forward with our plan for a phased and cautious return of a limited number of pupils to primary schools and early years settings from Monday, and students in Years 10 and 12 two weeks later.”