Homophobic bullying is still common in many schools and often goes unchallenged by teachers, a major report has found.
More than half of lesbian, gay and bisexual pupils have been bullied because of their sexuality, according Stonewall's new study.
It reveals that homophobic language is rife, with 96% of gay pupils reporting that they had heard comments such as "poof" or "lezza" used in schools.
Almost all (99%) of the more than 1,600 young people questioned said they had heard classmates saying phrases such as "that's so gay" or "you're so gay".
The schools minister Nick Gibb said homophobic bullying is completely unacceptable
While over half of gay pupils had faced verbal abuse, around one in six (16%) had been victims of physical abuse, and almost a quarter (23%) experienced cyberbullying, the School Report 2012 found.
But Stonewall also raised concerns that the bullying is being unchecked by schools.
Around three in five lesbian, gay and bisexual pupils who had been bullied due to their sexuality said teachers who witness the abuse do not step in to stop it, the report reveals.
Just one in 10 of those surveyed said teachers challenged homophobic language every time they hear it.
Half of the youngsters questioned reported that their schools said homophobic bullying is wrong - falling to 37% among those at faith schools, the study says.
Stonewall chief executive Ben Summerskill warned it was unacceptable that many gay young people are facing a "daily nightmare" of bullying, and said it was "deeply worrying" that this often goes unchallenged.
The report reveals that homophobic bullying often has serious consequences for the victims.
Nearly half (44%) said they had skipped school after being bullied, while a third (32%) had changed their future education plans as a result.
More than half (56%) said they had deliberately harmed themselves, and almost one in four (23%) had tried to take their own life, the report said.
Mr Summerskill said: "It's unacceptable that over half of gay young people face a daily nightmare of homophobic bullying, and deeply worrying that many schools and teachers still fail to challenge it effectively."
Stonewall's work with schools and local councils has helped to reduce the overall level of homophobic bullying "significantly", Mr Summerskill said.
He added: "We won't rest until every single gay young person in this country can walk through their school gates every morning without fear of being bullied just because of the way they were born."
Schools Minister Nick Gibb said: "Homophobic bullying, of any kind and of any child, is completely unacceptable. No child should have to suffer fear, victimisation or disruption as a result of bullying, either on or off school premises."
Tackling bullying and poor behaviour are key priorities for the Government, Mr Gibb added.
Shadow Education Secretary Stephen Twigg said every school should be a safe haven for pupils. "Stonewall’s School Report sets out challenges for schools, the Department for Education and Ofsted. It also makes recommendations for local authorities and academy chains - it’s vital that these are adopted."
Stonewall's study comes just weeks after an Ofsted report warned that name-calling is rife in many schools, but is often dismissed as simply "banter".
It found that pupils are using insults relating to sexuality, intelligence, race, appearance and family circumstances, with some saying it was acceptable if the words were being used between friends.
Ofsted said it was clear that pupils were using derogatory language outside the classrooms, such as in the playground, although at times it spilled over into lessons.
It warned that "gay" was often used as an insult, with one secondary school pupil saying it was used to mean "rubbish".