Primary school children are using homophobic insults without realising it, paving the way for later bullying, an educationalist has warned.
DJ Chris Moyles has been criticised for his use of the word 'gay'
Mark Jennett said teachers should not allow words like "gay" and "sissy" to be used as terms of abuse.
The terms made it harder for them to accept homosexuality when they later learnt what it meant, he added.
Mr Jennett told an anti-bullying conference in London that schools should log all homophobic insults.
'A bad thing'
The comments come after BBC Radio 1 DJ Chris Moyles was criticised by some groups for his derogatory use of the word "gay" on air.
But the corporation said employing the term as he did to mean "lame" or "rubbish" was widespread among young people and he had "meant no offence".
Speaking at the London conference, organised by the NASUWT teachers' union, Mr Jennett said: "It does matter if we are saying that homosexuality is a bad thing.
Bullying: Gay insults second only to weight insults
"If they were using the word 'girl' or 'Muslim' in a derogatory way we would challenge it and that would be the right thing to do."
Mr Jennett said figures showed 81% of primary school pupils identified the use of the word "gay" as "a means of attacking or making fun of someone".
He added: "By the time they find out that it means to be homosexual, they have already learnt that it means something bad."
On average, girls who find out that they are lesbian do not reveal this to anyone for three years, for fear of abuse or ridicule, Mr Jennett said.
Some schools had asked homosexual pupils to leave as they were unable to cope with homophobic bullying.
Schools in England are required to draw up an anti-bullying policy.
Mr Jennett said there should be explicit references to homophobia in all of these.
But some staff were also guilty of using insulting terms without realising it, he said.
"A lot of teachers say words like 'sissy' without thinking about it.
"One PE teacher I saw asked a group of pupils 'What's this, boys? A mothers' meeting?'"
Some local authorities in London are piloting a log book for all reported homophobic incidents, which Mr Jennett said should be extended to all schools, including primaries.
He said: "We should talk about sexuality, not sex: things like people's family lives.
"Primary school children are very strong on the concept of fairness. We should tell them just how unfair homophobia is."
A Department for Education and Skills spokesman said: "Bullying should never be tolerated in our schools, no matter what its motivation."
The Liberal Democrats have launched a campaign to stop homophobic bullying, with an online petition receiving more than 1,400 signatures.
The party's education spokeswoman, Sarah Teather, said: "Homophobic bullying is an issue for the whole school, not just for a victimised minority.
"This is not a matter of 'political correctness' but about pupil behaviour and the right of parents to feel confident that their child will be safe in school."