Pupils walked out of school instead of returning to lessons after hundreds took part in an anti-war protest.

Judi March, 42, said she was in Woodingdean yesterday when she was approached by several students from Longhill High School in Falmer Road, Rottingdean, and asked to sign a petition.

The pupils had earlier taken part in a peace protest on the school playing fields.

Mrs March said: "I struck up conversation with them and said it was good what they were doing because they do have a voice but the large majority of them just wanted the day off school.

"The trouble with this anti-war movement is they are just jumping on the bandwagon and are not representative of the true state of affairs.

"The pupils were really well behaved but they shouldn't have walked out of school. However responsibly they acted during the protest it was discredited by walking out of school."

About half the 1,200 pupils at the school took part in the demonstration which began before school started at about 8.30am.

Headteacher Geoff Ellis praised the students for acting responsibly and said most of them had returned to class soon after the demonstration.

He said: "One or two of them went home and got sent straight back by their parents. The protest did not last that long. The students who took part were quite responsible.

"There were just one or two silly ones who tried to get off home."

Meanwhile, pupils at Warden Park School in Cuckfield, who carried out a sit-down protest on the tennis courts, said they were threatened with suspension once they had gone back inside if they began protesting again. The school refused to comment.

Earlier this week, several pupils at Blatchington Mill School in Hove were suspended after staging a demonstration.

There have been reports some pupils have been texting each other mobile phone messages to encourage disruption in other schools.

Brighton and Hove education chief David Hawker said the council was happy to let pupils express their views, as long as it was done in a safe environment.

City headteachers would be receiving guidance from the education department next week on how to deal with further protests.

He said: "As with all of our heads, we are more than happy for pupils to express their views but what they must do is to do it safely and without disrupting their own or anyone else's education.

"A good example is what happened this morning at Longhill School in terms of the way they dealt with it.

"It took place on school grounds, safely and in an orderly way, before lessons started and once they had made their views known and felt they had been listened to they went back to their lessons.

"But no head teacher could sanction their pupils leaving the premises during school time. Of course it could create some health and safety issues too.

"We will be sending out some straightforward guidance to heads next week and I'm confident they will handle it sensitively."