The government may be forced to drop plans for all primary school pupils in England to spend at least a month in class before the start of the summer holidays, as headteachers welcoming back the first groups of pupils following lockdown warned that the idea was “ridiculous”. The initial phase of the government’s controversial reopening plans got off to a patchy start with many primary schools remaining closed to further pupils. For those that opened, attendance was as low as 40% in some, rising to 70% elsewhere. In some regions, as few as one in four state primary schools were reported to be open to more pupils on Monday than before, and just one in 10 in some local authorities. Most schools have remained open during the crisis for children of key workers and vulnerable pupils, but from Monday primary schools across England were asked by the government to open more widely and admit pupils in nursery, reception, year 1 and year 6, despite opposition from teaching unions and some scientific advisers. While media coverage showed returning children queueing 2 metres apart outside their primary schools for the first time since the gates closed on 20 March, it was clear that many parents were not ready to send their children back and some councils advised against premature reopening to more pupils. Geoff Barton, general secretary of the Association of School and College Leaders, said reports from members suggested the picture on the ground was “very mixed”, depending on differing local authority approaches, space constraints and staff availability. “This means some schools will not open this week, and there will be schools which are simply unable to bring in all the eligible year groups, that is reception, Year 1 and Year 6,” he said. “The expected level of pupil attendance is also highly variable, and we are hearing that it ranges anywhere between around 40% and 70% of the eligible pupils. It is likely this will increase as time goes on and more parents become confident about sending their children to school.” While there were no definitive figures on the number of schools that opened more widely and pupil attendance, a survey carried out by the Teacher Tapp app found that just 26% of state primary teachers said their school would open to more pupils on Monday – a figure close to that suggested by government sources last week. But as this week progresses, more than 50% of state primary teachers said their school will have reopened by Friday, and by next Monday the proportion will have risen to more than three-quarters of schools. While school leaders were satisfied with the plans for physical distancing they were able to put in place for the year groups due to return first, a number told the Guardian they were “at capacity” and there was no way they could fit all primary year groups in before the summer holidays. “It’s not going to happen,” said Richard Sheriff, chief executive of the Red Kite Alliance, which runs nine primary schools and four secondary schools across Leeds and North Yorkshire. For most schools, who are having to split classes into groups of less than 15, there will not be enough space. “It’s ridiculous. It’s not possible,” he said. A BBC poll of 2,350 primary governors from the National Governance Association found that three-quarters thought it unlikely that all pupils would be able to return before the summer. Previously, the government made plain in its coronavirus recovery plan that it wanted “all primary school children [in England] to return to school before the summer for a month if feasible”. But in a sign that they are backing away from the proposal, the prime minister’s spokesman said it remained “under review” and added that the government accepted that some primary schools would not be able to reopen on Monday. “It’s hugely important that children do have the opportunity to get back into school and to learn but we are doing this in a very cautious and safe way. We fully understand that there will be some schools who feel that they need more time to prepare.” The spokesman also indicated that there was government backing for a call from Anne Longfield, the children’s commissioner for England, for children to get catch-up tuition during the summer holidays. “We are [looking at] what additional measures may be required to ensure every child has the support they need, including over the summer,” he said. The education secretary, Gavin Williamson, acknowledged continuing safety concerns among parents. “I recognise there may continue to be some nervousness among families, but I want to reassure parents – and those working in schools and nurseries – that the welfare of children and staff continues to be at the heart of all of our considerations,” he said.