Some schools in England could remain closed in September if the swine flu pandemic escalates over the summer, the government has admitted.
The Department for Children, Schools and Families (DCSF) said that, while it was expected schools and nurseries would open as usual at the start of the academic year, it could not be "certain what the situation will be" in the autumn.
Decisions on closures would be taken shortly before the start of the autumn term, a message to schools across the country from the department said.
The DCSF guidance, issued as many schools broke up for the summer today, said it was monitoring the spread of the H1N1 virus on a day-by-day basis. A message will be sent to schools in the last week of August telling them what to do at the start of term, it added.
The DCSF said: "As the summer term is drawing to an end, it is important to ensure that everyone will be in a position to know what will happen at the start of the autumn term.
"We expect that schools and early-years and childcare settings will reopen as usual but at this time we cannot be certain what the situation will be then; we will need to monitor developments over the summer, and take decisions based on the best advice available shortly before the start of term."
About 1,000 schools have already recorded cases of swine flu, although most have remained open, according to the DCSF.
The message to schools follows a warning from the government's chief medical officer, Sir Liam Donaldson, that up to 65,000 people could die from swine flu in the UK in a worst-case scenario.
A planning document published by the Department of Health yesterday suggested that if the current growth in cases was sustained, the number of cases could peak in early September, with up to 30% of the population suffering illness.
There are also suggestions the spread of the virus could begin to slow over July and August before a resurgence in the autumn when schools reopen.
Margaret Morrissey, of the lobby group Parents Outloud, said ministers should have closed schools across the country early for the summer.
"I do think the government has had a major event of mismanagement here. They should have shut down schools and public places, not for ever, but to stop the virus spreading," she said.
In swine flu hotspots, schools should remain closed until children had been vaccinated, Morrissey suggested. "We might have to, in some schools, keep them closed until the vaccine is in place," she said.
The campaigner also called for the government to hand money to employers so that their staff can stay at home with their children if they are affected by swine flu.
"We helped the banks out, how about helping parents?" she said.
"There could be a decision that schools have got to say to parents, 'If your finances can be supported, do you agree with having the school closed until the children are vaccinated?'"
But she added that if it was possible to open schools in September then that should happen.
At the start of the outbreak, affected schools were closed, but the Health Protection Agency is no longer recommending that approach because swine flu is now widespread within communities.
HPA guidance says: "People are likely to be repeatedly exposed to the virus in their everyday lives. Closing a school will no longer be effective in slowing the spread of the virus as people could still be exposed outside the school.
"In some special circumstances – for example, a school with children who are particularly vulnerable to infection – then school closures might still be recommended."
Parents expressed concern yesterday about the now rapid spread of the virus, and some admitted they were scared and unsure how to respond to the situation.
Gloria Newell, 49, a housing officer, who was picking up her nine-year-old daughter, Natasha, from St Mary's Church of England school in Islington, north London, said: "I am just astonished. The figures are quite shocking. There seems to be nothing really in place to cope with this. We have heard about a national vaccination scheme but we do not know when it might be in place."
In north London, another mother, Amal Khaireddine, 30, was concerned about her sons Joseph, five, Shamus, six, and Ryan, eight, all pupils at Hugh Myddelton school in Islington, where there had been several cases of swine flu. "They had sore throats and temperatures and I did what you should do and called the GP. They said … not to worry. But I think they should have been tested, some swabs should have been taken … all you are told is check the NHS website, but that is not 100% safe."
In nearby Culpepper Gardens, Richard O'Connell, 63, said he had taken his two-year-old grandson, Alfie, to the doctor because of a high temperature and had been told not to worry. "But you do worry because you don't know what to do … it's all very well telling people to look at the NHS website but what of those of us who do not have a computer?"
Anne Alexander, 62, a retired playschool worker from Highbury, north London, believed the publicity was causing "mass panic". Collecting her nine-year-old granddaughter, Niamh Stepto, from school, she said: "The reality is that it may only be as serious as normal seasonal flu."
Paola Domizio, a pathologist and mother of year-old twins Aron and Susha, said : "I'm undecided whether to panic or not. Certainly it is alarming that so many young children may be susceptible. But what can you do? Even if you keep them in all day there are no guarantees. If a vaccine is developed I suppose children will be vaccinated, but until then all you can do is follow the guidelines. So I can't say that I'm particularly panicking, although the figures do sound alarming."
