In early 2009 I decided that it was time for me to do something a bit brave. I sat down with the head at the school where I teach, told him I was gay, and that I wanted to be open about it with the students. He was incredibly supportive and welcomed my suggestion that I could, in addition, do a whole-school assembly to help raise the profile of the issue of sexuality and homophobia.

When it came to "coming out", I dithered for quite some time as I had no idea how to approach the subject. Eventually in a year 11 physics lesson a student noticed me absent-mindedly playing with my engagement ring (I had recently proposed to my boyfriend) and said "ooh watch out sir, if you drop that your girlfriend will be really angry".

I quietly replied "it's a he actually, I'm getting married to a man". A wave a silence swept the classroom, followed by a barrage of curious questions. "How come you're gay sir, you don't sound camp?" and "But you don't sound at all like [an openly gay student in the year]" or "Is it legal to marry a man then?" We spent a few minutes calmly discussing it and then carried on with the lesson without any problems - I even managed a proper plenary! I was truly relieved, and somewhat surprised that there had been not even the slightest hint of a critical or negative reaction. In fact one student, a very imposing Asian boy, said to me at the end of the lesson "seriously sir, that was big - pretty sick... respect for being honest."

Since then I've done short, age-appropriate assemblies to every year at school on the meaning of words such as "gay", "lesbian", "transvestite", "transgender", and about the effect of using "gay" as a derogatory word. I've done other assemblies on the structure and growth of the teenage brain and why it makes coming out particularly hard.

I've never received any negative feedback from a single student, teacher, or parent - quite the opposite in fact. I had one anonymous letter from a student thanking me for "making a huge difference to his life", and I've had a couple of students telling me they're gay, but that's about it. My sexuality is rarely discussed with students in class, but on the rare occasions it is relevant and called-for (eg they ask a me a direct and appropriate question) then it is easily and honestly dealt with. I even have friendly questions from colleagues about how gay marriages work, who proposes to who, and what the stand is these days on gay adoptions etc.

As it happens I was also once a student at this very same school, and being a boys comprehensive in the early 90s it felt like a pretty tough place for a kid who was confused about his sexuality. In those days the message came through loud and clear that gay = bad, whether it was from my peers calling each other "gay" or "queerboy" when someone got too close or did something annoying, or from PE teachers who criticised weaker boys for being "pansies". I didn't know anyone who was gay, my parents never talked about anyone gay, and the only gay people in the media were either incredibly camped up comedians and actors or radical and aggressive gay rights campaigners, and I knew that I didn't relate to any of them.

My family seemed to assume I'd get married at some point, and I wrongly assumed that I would horribly disappoint them if I told them I was gay. I couldn't bear the thought of talking to my friends, who I thought (wrongly again) might turn away from me. I kept all issues about my sexuality hidden from view, and while I very grudgingly acknowledged to myself that I might have "bisexual urges", I refused to admit that I could possibly be gay. This self-repression and confusion carried on in a different way through university, where I had girlfriends and boyfriends, but no relationship worked out as my intellectual conclusion that I refused to accept being gay conflicted with my true sexuality.

Finally, some years later two massive events shocked me in to truly coming to terms with my feelings. The first was my mother's death from lung cancer, and the second was my own diagnosis with a rare and potentially fatal liver disease that led to a life-saving liver transplant in 2009. The counselling I received during these difficult years helped me come to terms with my sexuality, and when I watched the inspirational film Milk (about the life of a gay activist in the 70s) while recovering in hospital I decided that I needed to do something to make sure no students at my school ever went through the same bad times that I had. I promised myself that no student should feel there was nobody to talk to or have to hide their true selves, and that every student should know at least one positive gay role-model.

My school already had an outstanding record on dealing with bullying and promoting equality, but I hope very much that my actions have made life just a little bit easier for gay students and made an already tolerant school that little bit better. I know there are other gay teachers who are afraid to be open about their sexuality, and I'd like to urge them all to consider it - do it for yourselves, do it for your students, and do it to reduce inequality and bigotry in the whole of society. This isn't about making an aggressive political stand, it is just that nothing fosters tolerance and understanding like getting people to realise they know and work with a person who is happily gay.

• David Weston is a secondary school teacher and an education consultant at Informed Education. You can follow him on Twitter @informed_edu.

Resources on Guardian Teacher Network

Tackling homophobia and creating safer spaces advice

Short video clips from Younthhealthtalk of young people discussing their experiences of sex and sexual health.

Schools out annual conference

The Schools Out annual Conference is held on Sat 4 February in London. It's well-known as a vital event for educators to meet and discuss equalities issues and LGBT (lesbian, gay, bisexual and transgender) inclusive strategies. This year educators will be exploring how to deal with all forms of prejudice though the LGBT lens - how to give our young people information and experiences so that they leave school free of prejudice and negative stereotypes. Speakers include a school inspector talking about how Ofsted wants to see diversity included in schools and Sarah from the Channel Four series My Transexual Summer. More details and booking info here. Also see Schools Out's new website for teaching resources the classroom.

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