Despite warnings not to skip lessons, pupils are co-ordinating a series of "school strikes" using text messages and internet message boards. Some anti-war groups are urging pupils to walk out of school on Wednesday to protest against Mr Bush's state visit at a rally in Parliament Square. They also hope pupils will attend the main demonstration the next day, which will culminate in a statue of Mr Bush being toppled in Trafalgar Square.
Politicians and headteachers have condemned the groups as irresponsible and warned pupils that any unauthorised absences from school will be treated as truancy.
Tim Collins, the Conservative education spokesman, said: "It would be disgraceful if children were permitted or encouraged to leave lessons to attend this demonstration. Anti-Americanism is not on the national curriculum and if teachers are condoning this behaviour it is they, not their pupils, who should be looking for something else to do next week."
Phil Willis, the Liberal Democrat education spokesman, said: "It's not my job to support children taking time off school. But clearly the arrival of the President at such an important time is an issue that is of interest to schools. If young people choose to attend these demos I hope that schools will look at that in a positive rather than a negative way." More than 10,000 school pupils attended protests this year in the run-up to the Iraq war. Some schools locked their gates in an attempt to stop pupils walking out. Police were called to some schools after pupils took their protest to the streets.
The Government warned parents yesterday not to allow their children to miss school to attend the protests. Headteachers have threatened pupils with detention or suspension if they boycott lessons.
A spokeswoman for the Department for Education and Skills said: "While we fully respect young people's right to protest, this should be done outside school hours. During the school day, we expect pupils to be in school. If a pupil is out of school without permission, the absence is, of course, unauthorised and parents should be informed."
John Dunford, general secretary of the Secondary Heads Association, said headteachers were responsible for ensuring pupils did not miss school. "This is truancy and would be treated as such by schools," he said. "The normal punishments for truancy would apply - depending on the individual school's policy. It could mean suspension but it's more likely to be detention."
A spokesman for the Stop the War Coalition said: "We do not advocate people leaving school to attend protests. People will decide for themselves what they want to do. The national demonstration on Thursday goes on until 7pm so that is the ideal opportunity for people to come after work or school."
Verity Marriott, 16, an organiser for Schools Against the War, which is part of the Stop the War Coalition, is co-ordinating "school strikes" next week across London despite warnings from her school.
"I think it is really important for people to express their opposition to the war," said Verity, who is a sixth-former at a north London comprehensive.
"Students will gain an awful lot from going on the demo. Education is not just about sitting in lessons. I'm going to be missing a politics lesson on Thursday to be part of the protest and I think I'll learn far more at the demo than by being in school.
"My teachers don't know that I'm going to walk out - although a think a couple probably have a pretty good idea."
Michael Higgs, 15, a GCSE student at Pimlico School in central London, plans to skip lessons. He said: "My parents are pleased I have got a political mind and I am speaking it. I am against the war and against George Bush's state visit to London."