The government should provide more detailed guidance on what constitutes a "safe staff-to-pupil ratio" at schools remaining open during the coronavirus crisis, heads have said.
New Department for Education advice published this morning, which states that there is "no specific target or limit" on pupil numbers, is "not particularly helpful", according to the Association of School and College Leaders (ASCL).
It has previously been suggested that the proportion of pupils attending open schools during the crisis should not exceed 20 per cent of the school population.
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Geoff Barton, ASCL general secretary, said it would be a "good idea" for the government to publish "more detailed guidance" on what would make a safe staff-to-pupil ratio, "so that we are prepared for any change in the situation".
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The guidance states: "There is no specific target or limit on children attending educational or childcare settings.
"If you think you have more pupils than you can manage with the staff available, and particularly if this is impacting on your ability to implement social distancing, you should speak to your local authority (or trust, if appropriate) about how this might be managed."
Mr Barton said: "This guidance is not particularly helpful as it establishes no parameters on what is a safe staff-to-pupil ratio in the current circumstances.
"At present, the number of pupils attending schools is very low so we do not expect that schools are likely to be in a position where provision is unmanageable within the available staffing resource.
"However, it would be a good idea for the government to provide more detailed guidance, based on public health advice, so that we are prepared for any change in the situation, particularly if there is any future scenario in which schools are partially reopened for greater numbers of children."
Paul Whiteman, general secretary of the NAHT school leaders' union, said: "'Children should stay at home' remains the best advice for everyone, to limit the spread of the virus.
"Fewer pupils, spread out across many schools, following public health advice strictly, is likely to be the best option for protecting the health of pupils and school staff and reducing the spread of the virus."
The Department for Education has been approached for comment.