A gay teacher who fought back against advice to keep his sexuality secret by coming out in front of his whole school last year has set up a network to encourage other LGBT teachers to do the same.

Daniel Gray will launch the initiative, LGBTed, next weekend at an event where more than 100 teachers, school leaders and other educationalists will share advice on being gay or trans role models in schools. It is being supported by Nick Gibb, the schools minister, who came out to his family as gay three years ago having been in a relationship with his partner, now husband, for 29 years.

At the event, which will coincide with the 30th anniversary of section 28, the notorious piece of legislation that banned local authorities from “promoting homosexuality”, teachers will receive training in being LGBT advocates and tackling homophobia.

“The aim is to be the role models we needed when we were at school,” said Gray, who co-founded LGBTed to provide support to teachers. “I remember being at school during section 28 and I remember how horrible it was to be bullied the way that I was. I was told by my teachers it’s just something that you have to deal with.”

Until February last year Gray had not discussed his sexuality at work, but to mark LGBT history month he came out to more than 1,000 students at a school assembly. “Most didn’t bat an eyelid. There were no cheers, no drama or anything like that,” he said, but it delivered a crucial message. “Young people who I’d never spoken to before started approaching me and having conversations with me. One student came over to me and said ‘oh my God sir, your assembly changed my life’, and scuttled away. It’s little moments like that that you don’t get in your career if you don’t open yourself up as a visible role model and lead by example.”

Almost half of LGBT pupils in Britain’s schools are bullied for their sexuality, according to research published last year by the charity Stonewall. It has warned of alarmingly high rates of poor mental health among LGBT students: four in five young trans people have self-harmed, according to the charity, while 45% have attempted suicide.

Teaching is behind many other professions in supporting LGBT equality, said Hannah Jepson, co-founder of LGBTed, who added that schools were still recovering from the legacy of section 28. “There’s still a taboo where people conflate sexuality with sex,” she said. “Also the education sector is so big and there are so many different areas – you’ve got teaching schools, academies, local governments. It’s certainly not a system that’s working cohesively together.”

Gray said he had received the support of his headteacher, colleagues and the vast majority of parents – but that not all schools were as inclusive.

The experience of LGBT staff varies widely, according to David Weston, chief executive of the Teacher Development Trust and an advocate for LGBT teachers. “I heard the other day about a headteacher who said, ‘I was going to announce my same-sex marriage to colleagues but the local authority, said oh no I don’t think you should do that’. I was recently contacted by someone who is on initial teacher training who was told quite explicitly, ‘don’t mention anything, you’ll cause yourself problems’. It’s definitely a mixed picture still.”

Gibb, who will give a video address at the launch, praised the event. “Through initiatives such as the leadership equality and diversity fund, we are supporting schools to increase the diversity of leaders,” he added.

• In the UK, the Samaritans can be contacted on 116 123 or email jo@samaritans.org. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is 13 11 14. Other international suicide helplines can be found at www.befrienders.org