Young protesters from Worthing High School left their lessons to march against the threat of war against Iraq.
They took to the streets as part of a nationwide series of demonstrations.
More than 150 pupils filled the road outside the South Farm Road school, waving banners and chanting.
Five police cars and several officers shepherded the pupils off pavements up to Broadwater Green for their own safety.
The demonstration was organised by head girl Laura Procter, who said the volume of support was unexpected.
The 15-year-old said: "Our headteacher has been very supportive. We did not know about the demonstrations taking place until Monday. A lot of schools are closing down to protest against war in Iraq.
"We wanted to get involved but it was such short notice to close down the school, we decided to protest in the street."
Laura said the police had also been helpful, calling her to confirm when and where it would take place.
"I hope I do not get into trouble but I think it is our right to protest and I'm pleased with the turnout."
Alison Beer, Worthing High headteacher, said: "Laura is a very sensible girl, very committed and I am utterly supportive of her right to stand up for what she believes in."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article