Ten years old? That has been the universally incredulous response I've had when telling people that my son's class at a state primary school is currently studying sex education. It was my first response too when the letter arrived inviting us to view some of the materials they would be using. My second thought was that the opportunity to sit with other parents and my son's form teacher in the school hall watching dirty movies was too weird and too full of comic potential to ignore.

So there I was, sitting at the back with my mates, while the normally reticent Mr S introduced the DVDs and tried to pretend that he had not drawn the short straw in having to host what was, undoubtedly, the parents' evening of his nightmares. He did a good job, making a few jokes to put us at our ease and assuring us that he had taught this subject to primary-age kids for many years, and that what we were about to view was about as good as a film can be that has to carry the conflicting messages that making love is a wonderful thing and on no account should they be tempted to try it.

I have heard a great deal of ill-informed criticism suggesting sexual information is being taught in schools without the context of loving relationships being reinforced. Judging by the material I saw, this is far from the case. In fact, so much of the ensuing DVD concentrated on friendship and love, and how touching was a natural part of everyday life, and how holding hands was just the best thing ever, that I began to wonder how on earth - in the remaining 10 minutes - the gulf could be bridged between stroking someone's grazed knee and going at it hammer and tongs. Then, with a suddenness that made me reel in my uncomfortable, undersized chair, there was a jump cut to a couple of animated characters - strange, featureless Morph-like creatures - humping and thrusting like there was no tomorrow.

It was all a bit joyless, like when you see deer rutting in a nature programme, and had I been a 10-year-old it would doubtless have made me think I'd want to steer well clear of that stuff for the foreseeable future, which is, of course, a jolly good thing. Then it was back to lovely, safe, real-life humans holding hands and smiling asexually, apart from one curious moment when a couple of actors told the camera why they enjoyed touching each other's bodies, which seemed overly frank of them given that no one had actually asked them.

I gave permission for my son to watch the DVD at school the next day. It seemed to me that it was, though patently a bit odd, completely moral and blandly informative, and on balance I felt I would rather he learned any sexual facts he hadn't already gleaned from the eminently sensible Mr S than his less informed playground mates.

A few days later, the school held an open afternoon, in which parents were encouraged to see the sort of things their children were learning in all areas of the curriculum. My husband and I went, amusing ourselves that the one subject that wouldn't be being taught that day was the one that all the parents were sniggering about. To our surprise, when we entered our son's class, we found 28 immaculately behaved, calm, sensible, not-sniggering children colouring in diagrams of penises and placing fabric fallopian tubes in their correct anatomical position on a chart. At the centre of it all was Mr S, an avuncular exemplar of cheery matter-of-factness, answering questions, correcting mistakes, making it all seem normal.

There is a moral in all of this, I think. Sex education is a big deal because we make it so; many parents seem to feel that because they weren't taught it at the age of 10, there must be something wrong with our children learning about it then. But every 10-year-old I know has some sketchy understanding, or, worse still, ill-informed curiosity about where they came from. Surely answering their questions at the age when they are first being asked, and in a relaxed, responsible and yes, relationship-based way, is the best chance we have of raising loving, respectful adults, and not the sort of prurient, childish people who sit at the back of the hall sniggering with their mates at the word penis ... like I did.

• Rebecca Front is an actor and writer comment@theguardian.com