As he watched the planes crash into the World Trade Centre on television, Anthony Stanton, headteacher of Simon Langton girls’ grammar, started rethinking school security. “Within minutes, I was reflecting on the implications for us,” he says “and how we could avoid making bad decisions because we hadn’t thought it through.”

The school now has a policy based on the possibility of an attack on Dungeness nuclear power station on the south Kent coast, or the contamination of air or water supplies. Mr Stanton and his staff have consulted with parents on the options, assuming that telephone lines might be out of action. “The potential for a radioactive plume is significant, but we could protect our girls for 24 hours simply by keeping them inside,” he says. The plan includes cutting off contaminated water supplies, and rationing the use of sealed tanks.

Kent County Council has recently dealt with anthrax scares, one involving pupils on a visit to Rochester cathedral, and has experience of dealing with unexploded bombs. The authority’s emergency planning officer, Nick Rowe, stresses the reliability of existing national and local contingency plans, and says there hasn’t been “a vast change since 911”. Council officers have been training headteachers to cope with two scenarios - a school coach trip crash, or an armed intruder in school.

“Our plans set out evacuation and care procedures,” says Nick Rowe. “It makes little difference what the cause is; the solution is the same.” The 1996 Dunblane shootings and the attacks on primary school pupils at Holy Cross school in Belfast have highlighted the vulnerability of schools. High fences and closed circuit television cameras are now the norm in parts of the country. But all schools may have to further develop their security strategies. Faith schools and those where one ethnic group predominates may feel particularly vulnerable; already, Jewish schools in the UK use a private security service.