They were among 200 students who staged a demonstration outside Blatchington Mill School in Hove, West Sussex, last week.

No others were excluded following the incident.

Parents of the six, whose suspensions last until they begin their GCSE exams, said their education had been needlessly disrupted.

But the school's head teacher, Neil Hunter, said the pupils had been excluded because of an "accumulation" of incidents.

'Vindictive'

Sally McMurray, whose 15-year-old daughter Sarah was among them, called the decision "vindictive".

She said the pupils' actions were reasonable in the context of the government's build-up to war.

Mr Hunter defended the suspensions, saying: "As a school, we were not against students making a protest.

"On the contrary, we are very proud the students were concerned enough to do something."

Before the protest, last Friday, the school had allowed those against war to circulate a petition, which was reported by the local press.

Mr Hunter said: "I told them it would be dangerous if they staged a walkout and left my duty of care. But some students felt they wanted to do something else.

"We are not against students expressing a view. However, the actions must be something which does not put the health and safety of students in danger."

The Blatchington Mill walkout followed similar incidents earlier last week in London, Birmingham, Leeds, Sheffield, Liverpool, Cambridge and Milton Keynes.

Hundreds of schoolchildren went to Downing Street, while more than 200 children - some as young as 13 - are protested outside the Houses of Parliament.

A spokesman for Brighton and Hove City Council said the Blatchington Mill parents could make an appeal, to be heard by the school's governors.