Three quarters of young men who are gay or bisexual don't receive any information about same-sex relationships at school, with two thirds going without HIV testing advice.
The research, by the National AIDS Trust, coincides with figures which show HIV diagnoses among males aged 15 to 24 who have sex with men have doubled in the past 10 years.
Young men who have sex with men (also known as MSM) are more likely to experience a range of other health issues such as poor mental health and problematic drug and alcohol use, which are associated with HIV transmission risk behaviour.
The survey, which questioned more than 1,000 young MSM, is the largest of its kind ever conducted in the UK and found a third had not received any information on HIV transmission and safer sex during sex and relationships education (SRE) in school.
James Hanson, who was diagnosed with HIV at the age of 18, said he knew "very little" about the virus.
"I remember very clearly some awful sex ed lessons at school", he says. "I was shown a video of a typical family, where the whole family paraded around house naked and taught that sex is for a man and women for pleasure and have babies. I was never taught of the love between two men or two women.
"I was having feelings I didn’t know what to do with and I felt so isolated because it was never spoken about. Looking back now I feel let down."
More than half had experienced homophobic bullying and discrimination, with nearly one in four being bullied at the hands of teachers or another adult at school.
Nearly 30% of respondents didn't know how HIV could be transmitted, with 29% not knowing whether it could be caught through kissing. Almost three quarters of survey respondents (71%) did not know or were not sure that "if you think you have put yourself at risk of getting HIVyou can take a drug called PEP, which can prevent HIV infection if taken within 72 hours".
Commenting on the report, Lord Norman Fowler, former secretary of state for health, added: " We are missing a key opportunity to give our young people the support they need.
"Much more must be done if the next generation are to have access to the information they need to protect themselves from HIV and to end the health inequalities they currently face."
A spokesperson for the Department for Education said: “Homophobic bullying can blight young people’s lives. It not only affects young people’s happiness and achievement at school, but can have severe consequences for their mental health.
”That’s why we made a tackling homophobic bullying a priority in the Coalition Agreement and since then we’ve invested in projects to train more teachers on tackling homophobia in the classroom and set out clear guidance on the importance of tackling all types of bullying, including homophobic bullying.
“We’re pleased that teachers are now reporting lower rates of homophobic bullying compared to five years ago and greater confidence in tackling this bullying.
”Of course there is no room for complacency which is why we recently announced a £2 million fund to support projects to combat this bullying in our schools and take us step closer towards our goal of eradicating this bullying from our classrooms.”