One morning, halfway through my 15 years as a headteacher, a member of staff made an appointment to see me. She told me that she was on the receiving end of some unpleasant sneering from some Year 11 pupils. “About what?” I asked. “My sexuality,” she said.

She’d walk down the corridor and, just occasionally from this group of pupils, she’d overhear lewd remarks or sniggering innuendos. Apparently, one of the group had seen this teacher shopping with her partner the weekend before, and then the snideness began.

She was surprised, she said bleakly, in a school like ours, where she had listened to me talk so much of inclusive values, that a matter so personal should be allowed to become public.

I was, of course, mortified, disappointed, upset. Her comments exposed a fissure at the core of our ethos, a disconnect between what we said we stood for and what was clearly happening in the corridor. And whether it was happening to a member of staff or a pupil, this was unacceptable.

From that point onwards, with all our students, of every age and background, I’d give an annual assembly in which I showed the photograph you can see above. And here’s the gist of what I said:

“If you’re like me, you’ll think there’s nothing more boring than someone showing you pictures of their holidays. So, I want to show you a photo. And it’s of one of my holidays, taken on the last day.

“You can see me, my wife Philippa; you can see my two sons standing in the back row. And you can also see my nephew, David with his partner, both holding the two sons they have adopted.

“This is our family: people of different colours, different faiths, and – if it matters – of different sexual orientation.

“And if, when you look at that photograph, you have an issue with it – the colour of the skin, the nature of the relationships – then the problem, if you don’t mind me saying so, is you.

“Because this is what families in the modern world often look like. They’re more varied, more diverse than at some points in the past.

“And, frankly, the modern world needs people who see beyond colour, who don’t judge by gender, class or sexuality.

“This photograph reminds me what my family looks like. It’s what many families today look like. And here’s the thing: I wouldn’t want it to be any different. And I couldn’t be prouder of each of them for who they are.”

Our annual pupil surveys showed that, of the many hundreds of assemblies I delivered in my time as a school leader, this was the one that was remembered, the one that was most appreciated – by pupils and by staff.

You’ll know why I revive memories of that assembly now.

There are ugly scenes in Birmingham, with children and adults feeling intimidated on their way to and from school, a place which should be an oasis of calm learning, fun and laughter.

And it seems to me that what these schools are doing is no different from what I did in those assemblies – they are teaching that there are different forms of family, and that all of them can be equally as loving, supportive and happy.

In doing that they are sending out a clear message to their pupils about the values of our society – about being welcoming and inclusive to all people of all backgrounds, of accepting people for who they are.

Granted, these are primary schools and mine was a secondary school, but why should that make any difference? This is about educating young people about relationships, not teaching them about sex, and it seems suitable and appropriate to talk about inclusivity to children of all ages.

But the problem for these schools – and by extension, all primary schools – is this: what specifically are they expected to teach?

Because the government doesn’t seem all that clear on this important point. There is the new guidance on relationships education in primary schools which comes into force next year and which makes a reference to different types of families, including those with LGBT parents, but doesn’t specifically say whether primary schools are expected to teach about same-sex parents.

And then there are statements from Education Secretary Damian Hinds about school leaders being best placed to make decisions, and primary schools being “enabled and encouraged to cover LGBT content if they consider it age appropriate to do so.” Basically, it’s up to you folks.

Of course, school leaders make decisions about all sorts of things all the time. But this is a bit different.

By just including LGBT families as an example of the different types of family primary schools might talk about, it becomes an individual headteacher’s decision about whether to use that particular example or not. This means they’re the ones who take the flak from parents who disapprove.

If the government were to be clearer that primaries must talk about LGBT families, that would take some of the pressure off individual heads.

That is why I was pleased to see the comments of Conservative leadership contender Michael Gove, reported in Tes, saying that if he becomes prime minister he would make it clear that it is a government requirement for primary schools to teach children about LGBT relationships.

He said: “I believe that teaching children that some people have two mums and two dads is an important part of preparing them for life in modern Britain. Indeed, many children in primary schools will have classmates with same-sex parents.

"While it should be for primary schools to decide how to introduce this teaching as part of the curriculum, I will be clear that teaching the topic is a government expectation. In doing so, we will send a clear message that any protests or disagreement should be directed at the government, not individual headteachers on the frontline.”

I frequently disagreed with the things Michael Gove said and did when he was education secretary but, on this point, he is 100 per cent right.

This whole situation is crying out for a clear and unequivocal statement from the government, one which gives clarity to schools, and affirms that these values are so important they should be a core part of what we teach our children.

It’s hard to argue against an inclusive, modern, forward-looking society. Education – at all stages – is where we prepare our children and young people to take their place in such a world.