School children across the UK have walked out of lessons to stage demonstrations against the start of the war with Iraq.
Hundreds of students are in Westminster
Hundreds of children are among crowds protesting at Westminster.
School children have been played a big part in many demonstrations across the UK while others have staged their own protests at their schools.
Student leaders urged students to join the protests across the country.
Mandy Telford, president of the National Union of Students (NUS) said: "The NUS is strongly opposed to a war on Iraq.
"We do not believe that destroying one of the oldest civilisations in the world with bombs and killing thousands of innocent people is the best way to effect change.
"Saddam Hussein's regime is a brutal one, however there must be a more sophisticated way of bringing about change than heaping further misery on a country that has already endured waves of air strikes and sanctions.
"Freedom for the Iraqi people must not be brought about by needless bloodshed."
School children picketed many schools across London this morning to gather protest supporters, because they said they thought their teachers would stop them leaving if they went inside.
Sinead, who is 18 and from a north London sixth-form college called Le Swap, is at the Westminster demonstration.
"When I woke up this morning, I was so incredibly nervous. I felt sick," she told BBC News Online.
"Tony Blair might have got the Commons' vote but so many people are against this. People are angry and frustrated at being ignored."
Sinead said about 100 chidren from her college walked out and headed for Parliament.
Sixth-former Sam Beste, from Fortismere School in north London, has organised many protests against the war.
Young people came from across London
He is staging a demonstration with dozens of others in Muswell Hilll before heading for Westminster.
He said many older children were trying to walk out of school this morning.
"Many of us thought the war was inevitable but we are not going to start backing it now it has started," said Sam.
"People are angry. We must keep trying to stop the war"
Henna, who is 18 and from Coombe Girls' School in New Malden, is part of a network of schoolchildren from south London protesting in Westminster.
Standing outside Tony Blair's house is a way to show him what we think
"I'm here to get my message across. Two million people walked through London against this but war is still going on.
"Standing outside Tony Blair's house is a way to show him what we think."
In Carlisle, the police were called to a school after hundreds of pupils staged an anti-war demonstration.
Around 200 11-to-16 year olds from the Caldew School in Dalston marched into the centre of the village chanting anti-war slogans.
Head teacher Andy Abernethy said he supported the students' rights to demonstrate, but could not rule out disciplinary action against some of the protestors.
A Stop the War demonstration in Edinburgh caused extensive disruption in the city centre.
The demonstrators were mainly school-age youngsters who gathered near the Scottish Parliament and have since split in to smaller groups which have been stopping traffic in various locations.
It is thought there have been several arrests.
Stirling University was closed due to protest action.
There were two separate demonstrations in Belfast with more than 1,000 students and schoolchildren mounting a sit-down protest, blocking the road outside Queen's University.
In Nottinghamshire, more than 100 pupils walked out of lessons at West Bridgford School to stage a demonstration on a nearby playing field.
They are now back in class.
In Manchester, about 200 school children joined a big demonstration.
In Sheffield, two schoolchildren were arrested by police for alleged criminal during a demonstration.