By Sean Coughlan
BBC News Online at the NUT conference in Harrogate
Teachers are warning that ethnic tensions in schools are being aggravated by the rise in far-right political parties.
Teachers warned against the growth in support for the far right
The National Union of Teachers' annual conference heard that the British National Party was recruiting among school children.
Teachers said racist leaflets were "poisoning the atmosphere in schools".
When such leaflets appeared in schools, the levels of "racial violence" increased, said delegates.
A teacher from Oldham told the conference in Harrogate that his school had to be closed for a day while swastikas and racist graffiti were removed from walls.
There were also claims that children as young as nine were being recruited by the extreme right-wing.
Delegates heard accusations that the BNP was now "suited and booted" and undergoing an image "make-over" to appear respectable - but that it remained a party of intimidation and race hatred.
Maureen Skevington spoke of the "enormous fear" that the BNP had created when it stood for local council seats - and the relief when candidates were defeated.
Bryan Beckingham told the conference that the threat of the far right must not be "swept under the carpet".
Whenever their recruiting leaflets appeared, he said, "racial violence increases in schools".
"The BNP isn't a threat, it's a reality," delegate Sue McMahon told delegates.
The conference also urged schools in Britain not to follow the example of the headscarf ban in France, which had caused conflict with some Islamic pupils.
There were also claims that media coverage of asylum seekers was provoking an increase in racist attitudes among school children.
The conference of the biggest teachers union backed a motion warning against the rise of the extreme right - and urging opposition to the BNP's electoral ambitions in forthcoming elections.
John Bangs, the NUT's head of education, said: "We've had some incidents in the past where BNP paper sellers have targeted particular schools.
"But particularly in some of the northern towns there has been an increased BNP presence and it affects fundamentally the relationship of young people to each other in schools."
Mr Bangs said there had been complaints and there was a "general anxiety" about their presence.
He said they would be consulting the police over whether the BNP were breaking the law.