“Terrorists have a method to their madness - when they find something that works they repeat it,” said Graham Allison, director of Harvard university’s Belfer centre for science and international affairs and a security adviser to the Democratic presidential candidate John Kerry.

Ron Astor, professor of education at Southern California university, said he feared a “contagion factor” that would lead some groups to see attacks on schools as “a way to create international attention through horror”.

Stephen Heyneman, Vanderbilt university’s professor of education, said US, British and other European international schools in particular faced a risk of attack.

A US government official, who declined to be named, said many American schools abroad, particularly in the Middle East, were already on heightened alert since the September 11 attacks on New York and Washington in 2001.

Mr Allison, a former assistant defence minister, called the Beslan siege “worryingly well-organised”. Militants planned the attack well in advance, booby-trapping the school during summer construction work. They got through checkpoints undetected, and the siege took place 200 metres from a police station.

Concerns have also been raised about domestic US schools. A draft copy of a report by a non-partisan coalition of education, government and business leaders, passed to The TES, found nine of the 20 largest education authorities are unprepared for an attack.

“Large school systems need to do more, often much more,” said the report, which singles out Chicago as a “picture of failure”.

In March 2003, the White House earmarked $30 million (pound;17m) to boost schools’ emergency plans.

School officials at Fairfax County, near Washington DC - seen in the report as the “best prepared school district” - rehearse attack scenarios with police.

In Michigan, the first state to designate schools as part of its “critical infrastructure”, schools co-ordinate plans with local emergency services and provide maps of their layout.

Authorities’ ignorance of the number of hostages in the Beslan siege and the layout of the school has been seen as a key factor in the huge loss of lives.