Almost two thirds of homosexual pupils in Britain's schools have suffered homophobic bullying, a survey suggests.
New anti-bullying guidelines are being drafted
Almost all of those had experienced verbal bullying but 41% had been physically attacked, while 17% said they had received death threats.
The study was done by the Schools Health Education Unit for campaign group Stonewall, which said adults in schools were often behind the bullying.
The government said that all forms of bullying were unacceptable.
Stonewall said the report, on the views of 1,145 young people, was the largest poll of its kind ever conducted in Great Britain.
It presented "a shocking picture of the extent of homophobic bullying undertaken by fellow pupils and, alarmingly, school staff".
"Even if gay pupils are not directly experiencing bullying, they are learning in an environment where homophobic language and comments are commonplace," the report said.
"Ninety-eight per cent of young gay people hear the phrases 'that's so gay' or 'you're so gay' in school, and over four fifths hear such comments often or frequently."
Half of teachers had failed to respond to homophobic language when they heard it and less than a quarter of schools had told pupils that homophobic bullying was wrong.
There have been ongoing complaints from Stonewall that faith schools in particular do nothing to deter homophobia.
Seven out of 10 of the survey respondents who had experienced bullying said it had adversely affected their school work.
Half of those bullied said they had missed school as a result.
When schools did intervene, the report said, young people were 60% less likely to be bullied.
The report highlights numerous examples of youngsters' experiences of verbal and physical assaults.
Stonewall's chief executive, Ben Summerskill, said: "These deeply disturbing figures should serve as a wake-up call to everyone working in education.
"This remains one of the few sorts of bullying about which too many schools still take no action.
"It blights the lives not just of gay children but of thousands of pupils perceived to be lesbian or gay too."
A Department for Education spokesman said all forms of bullying were unacceptable.
"We are pleased that Stonewall have highlighted this important issue and we look forward to continuing to work with them in the future.
"It is important that pupils tell someone when they are being bullied and that teachers take firm action.
"That is why we have given new powers to teachers to ensure they can do so. No pupil should suffer the torment of bullying."
Call for action
Liberal Democrat education spokeswoman Sarah Teather said that, in schools especially, young people should feel safe and able to express themselves.
"Whether a young person is gay, seen as being gay or has gay parents, homophobic bullying can make their life a misery.
"All schools, including religious schools, should have anti-bullying policies that specifically address homophobic bullying."
Ministers must match kind words with action.
"Until schools are compelled to monitor and tackle homophobic incidents, as they must racism, it will not get stamped out."