, a biopic of the first openly gay man to be voted into public office in the US.
Harvey Milk stood for election in the 1970s, at a time when campaigns were taking place across the country to outlaw homosexual acts and repeal equality laws.
In a now-famous speech, he said: "Gay brothers and sisters, you must come out. Come out to your parents. I know that it is hard and will hurt them but think about how they will hurt you in the voting booth. Come out to your relatives. Come out to your friends, if indeed they are your friends. Come out to your neighbours, to your fellow workers, to the people who work where you eat and shop.
"Come out only to the people you know and who know you. Not to anyone else. But once and for all, break down the myths, destroy the lies and distortions. For your sake. For their sake. For the sake of the youngsters who are becoming scared by the votes from [homophobic states] Dade to Eugene."
Watching this was electrifying. Thinking back to my own confused and difficult teenage years, I remembered having nobody to relate to. I remembered how scared I was by the casual homophobia around me. Listening to that speech, I vowed to stop hiding my sexuality at school.
When I finally got back to work, I approached my headteacher, who was totally supportive. We agreed that if it came up in conversation with pupils, I would simply be honest. We also agreed that I would lead an assembly on the changes to gay legislation and homophobic bullying.
But nothing actually happened until early 2010. In a run-of-the-mill physics lesson, I was fiddling around with my new engagement ring (I was due to have a civil partnership later that year). A sharp-eyed student noticed this and, I suspect in an attempt to distract me, asked me if I was engaged.
I replied that I was, and he followed up by advising me: "She'll be angry if you drop it, Sir."
I replied: "It's a he, but yes, he would be angry."
I waited. There was a pause, followed by questions.
"So are you gay then, Sir?" "How come you've got engaged, I didn't think men could get married?"
I answered these queries and a couple of others, then we got on with the lesson. At the end, a student came up to me to say thank you. I braced myself for further reaction but none came.
Not long after that I took the assembly. I was able to begin by saying: "As many of you know, I'm entering into a civil partnership with my boyfriend later this year, so I wanted to talk to you about gay legislation and explain why this assembly would have been illegal 15 years ago."
It went well and a couple of students and colleagues thanked me at the end. But most pupils didn't seem to bat an eyelid. Again, I braced myself again for repercussions, but none came. No negative comments from students, from colleagues or from parents. In fact, there wasn't much follow-up at all.
Together we stand
That was until August, when I received the email from a former pupil. I was so touched that I shared it on Twitter; I thought other teachers would appreciate this lovely note. To my astonishment, the tweet went viral. It was shared by journalists, comedians and actors, and retweeted more than 3,000 times.
The former student and I were invited on appear on ITV News London and BBC Radio 5 Live. I was interviewed by several websites and newspapers and even had a phone call with the producers of The Ellen DeGeneres Show in the US.
The reaction was incredibly positive. What was particularly striking was how many students and teachers got in touch. Most pupils said they wished they'd had a gay role model at their school and a lot of gay teachers said they felt as though they might now be prepared to come out to pupils.
Interestingly, some teachers who were already out at school said they had not experienced any issues at all, although some who were yet to reveal their sexuality were afraid of what might happen.
This was a wake-up call for me. No teacher should have to hide who they are and young people shouldn't be denied the openly gay role models they need to be confident citizens. Lesbian, gay, bisexual and transgender (LGBT) teenagers still have worryingly high levels of anxiety, bullying, depression and self-harm. If we LGBT teachers can overcome our own fears and be out, and if our colleagues can support us, we could make society a better place for everyone.
David Weston is a former maths and physics secondary teacher. He is now the chief executive of the Teacher Development Trust and a primary-school governor