Students have been staging a day of action in protest across the UK against proposed increases in university tuition fees.
Thousands of students staged sit-ins, occupations and walkouts at universities and colleges, with pupils also staging protests at schools.
The protest was organised by the National Campaign Against Fees and Cuts (NCAFC).
It says at least one in 10 students is planning to take part.
The biggest demonstration took place in central London - but protests have been seen in many other cities.
Around 2,000 people gathered in Bristol to protest.
The protesters assembled outside Bristol University's Senate House in Clifton as part of widespread action.
They then marched on to the Wills Memorial Building. Roads in the area were blocked by police and diversions put in place.
A police spokesman said four people had been arrested in connection with public order offences.
Those present included students from the University of Bristol and the University of the West of England.
Students from City of Bristol College were also there, along with pupils from St Brendan's Sixth Form College and Bristol Grammar School.
Thousands of students have marched through central Manchester.
Schoolchildren walked out of lessons to join a column of university students on Oxford Road. Another protest took place in Bury town centre.
The column of students filled Oxford Road as they began marching from the universities to the south of the city centre at lunchtime.
Banners included "fight business greed make them pay", "Tory scum here we come, Dumbledore will be ashamed" and pictures of Nick Clegg with a Pinocchio nose.
Pupils in their school uniforms, students, and some parents took part in the marches, which were chaperoned by police.
Students have occupied part of the University of Birmingham's Great Hall.
Up to 40 students who got inside the Aston Webb building earlier say they are planning a 36-hour sit-in.
They unfurled a banner calling for the university's vice-chancellor to resign.
Student Adam O'Connell said they had had messages of support from other student occupations that had started around the country.
"I think direct action is the only way," he said.
About 2,000 students in Sheffield, including hundreds from a secondary school, have joined protests in the city.
Some 300 pupils, mainly sixth-formers, walked out of King Edward's School despite a warning that their absence would be considered unauthorised.
They joined other students on a march to a rally at Sheffield Town Hall.
Sheffield City Council leader Paul Scriven said the students were "taking part in the democratic process".
Mr Scriven, a Liberal Democrat, said: "As long as they are not going to cause disruption to anyone else then it is absolutely right that their voice is heard."
More than 2,000 students from across Merseyside staged a protest in Liverpool.
Students from Liverpool's universities and prospective students from colleges and schools gathered at the Liverpool Guild of Students at 1100 GMT.
They marched to Liverpool Town Hall, where they were addressed by Labour councillor Nick Small.
Some students later staged a sit-down protest at the top of Bold Street.
The group of about 300 people blocked three major city centre roads to traffic - Bold Street, Berry Street and Renshaw Street.
Sit-down protests were earlier staged at Lime Street station and outside the town hall.
About 1,000 students have been taking part in a protest in Leeds over university tuition fees, with dozens of youngsters also leaving one school.
A spokesman for Leeds University Against Cuts (LUAC), said the protesters were making their way to Victoria Gardens.
And up to 60 students walked out of Allerton Grange School in the north of the city in support of the action.
West Yorkshire Police said they had a "large policing presence".
Ian Pattison, LUAC spokesman, from the LUAC, said they expected students from "a whole host" of educational establishments to join the city centre protest.
Hundreds of students from universities and sixth form colleges in Cambridge are taking part in protests.
A number of students climbed over railings and scaled scaffolding at the University of Cambridge's Senate House to erect banners.
Students from Parkside Community College walked out onto Parker's Piece to show their support.
Nottingham students, including the reigning Miss England, have been voicing their opposition to the planned rise in tuition fees.
About 100 students also intend to hold a "teach-in" later and occupy a room at Nottingham University.
Jessica Linley - crowned Miss England in September - has spoken in support of the action, calling the government plans "unacceptable".
Miss Linley, who is studying law at Nottingham University, said: "Raising tuition fees will ultimately lead to more educational inequalities and we will see a dramatic fall in the number of students from disadvantaged backgrounds going to university."
Sussex Police said up to 3,000 students paraded through Brighton city centre as eggs and fireworks were thrown.
Protesters gathered outside Brighton University buildings in Grand Parade and chanted "Shame on you" to those inside as 15 people went in.
One Brighton University student, who gave her name only as Charlotte, said: "I'm really worried about education. Even though with increased fees, more money will be put in, less money will be spent on the actual teaching and the quality is going to suffer."
More than 70 students have taken over a lecture theatre at Warwick University.
The rally in Warwick has been largely peaceful so far, police said.
But minor scuffles between students and security guards have taken place outside and inside the Centre.
It is thought some students were planning to stay overnight.
Students occupied a room at the University of Plymouth.
About 200 students from King Edward VI Community College in Totnes also walked out.
More than 300 students turned out for a protest at Princesshay in Exeter and brought buses to a standstill.
Protesters at the University of Plymouth handed handed a list of demands to the university's vice chancellor, Professor Wendy Purcell.
In Durham students assembled outside the Town Hall before marching through the city centre.
Guy Hutchinson, a post-graduate at Durham University, said: "Protesters are walking through the streets of Durham. There are school students, university students and a few university lecturers.
"I'm here because I'm very concerned at the cuts in education and also the way that university education is being reframed as being of benefit to the student rather than being in society's interest."
About 300 secondary school students marched on County Hall in Derbyshire.
The students left classes at Highfields School in Matlock at about 1100 GMT. Some of the group were invited into the headquarters of the county council to discuss their concerns.
There was also a walkout at Queen Elizabeth's Grammar School in Ashbourne.
Police closed a main route into Cornwall's only city as more than 100 students carried out a protest march.
The A390 in Truro was closed while protesters walked from Truro College on the city's outskirts to County Hall.
As well as the Truro march, another group of 40 people protested at the Tremough Campus of the Combined Universities in Cornwall at Penryn.
Another protest was held in Falmouth. The marches were against government plans to increase tuition fees.
Hundreds of A-level students in Colchester, Essex, staged a protest.
The students marched from North Hill to the Town Hall and are planning to visit the town's Liberal Democrat MP Bob Russell to voice their concerns
BBC reporter Marianne Bradley said: "In contrast to the violent scenes in London the students protesting in Colchester simply showed youthful enthusiasm and passion for their cause.
"Teenagers from three schools, normally pitted against each other in league tables, came together outside the sixth form college and marched carrying placards, escorted by mounted police, through the town centre.
"Bemused shoppers stopped and listened to their chants of 'Education is a right not a privilege' and office workers came out onto the streets; many of them taking photos of the protest on mobile phones."
Around 300 Cardiff students staged a sit-in before marching on the city centre.
The protesting students took over the main building of Cardiff University to reject the UK government's plans to impose £4.3bn cuts to higher education and the pay awarded to its senior administrators.
They then marched along Park Place towards the city centre, bringing traffic to a standstill.
At Monmouth Comprehensive, sixth form students staged a protest with banners.
Pupil Anna Burn said: "I think it's really important that we show the government exactly how we feel because if they understand how passionate we are about education, they are much more likely to listen in the future."
Students and lecturers at Aberystwyth University held lectures and seminars on the streets in the town's Bank Square.
Scots students at Scottish universities have not paid tuition fees for a decade but there is still concern and anger about the future of higher education, says BBC correspondent James Cook.
In central Edinburgh some 200 students protested outside the Liberal Democrats' Scottish headquarters.
The road was closed as they chanted slogans and listened to speeches before handing a letter to staff and then marching back to Edinburgh University.
Jenna Spence, 20, a sociology student at Edinburgh University, said her vote for the Lib Dems in the general election had been repaid with a "kick in the teeth".
"We're particularly annoyed at Nick Clegg's pledge to vote against any increase in fees," she said, adding: "It's not actually translated in reality."
Demonstrations have also taken place in Glasgow, where organisers claimed some 350 students and school pupils marched to the city centre for a rally in George Square.
Brandishing banners bearing the slogan "no cuts", the protestors said they were angry not just about education policy but also about cuts to public services.
Around 30 students also occupied the Royal College building at Strathclyde University.
The Scottish Government is currently preparing a green paper on the future of higher education.
It is due to be published before the end of the year but ministers have already ruled out a return to up-front tuition fees, leaving a big question mark over how the sector will be funded.