When I’m tutoring on a writing workshop for museum and gallery professionals, we always advise participants against using the passive voice. It’s evasive, we say. It suggests to the visitor that you’re hiding something. Who exactly is doing or saying it? The visitor wants to know.

And that’s how I felt when I read that notice as I entered the Hayward Gallery on the last, crowded weekend of the Walking in My Mind exhibition, accompanied by my eight-year-old twins. Who didn’t consider the work suitable for my kids?

Not me. And certainly not the other parents who were there that weekend. Every single family I saw nodded at the notice, then dragged their toddler or teenager into the gallery, stalwartly ignoring it.

The particularly offending item was a work by Jason Rhoades called The Creation Myth. In a huge room as crowded as a jumble sale, there were, if you looked carefully, some images of women’s genitals in the style of pages torn from a pornographic magazine. (There was an additional notice outside this room, with PARENTAL GUIDANCE in big red letters –
‘Visitors should be aware that this work contains sexually explicit images. This work is not suitable for children. To by-pass this work, please retrace your steps …’)

The problem was, the only reason my kids looked carefully was to find what they weren’t supposed to see. ‘What’s not for children?’ they pestered me. If there had been no notice, they wouldn’t have noticed. And even when they did find the offensive images, they just glanced and moved on to more interesting items – the toy train with a stuffed snake on top, for example. My teenager, in contrast, would have stuck by anything suggesting sex. But I don’t think the parental guidance notice was directed at 16-year-olds.

This isn’t the first exhibition where my kids have been warned off. I remember the 1997 Brit Art exhibition at the Royal Academy, where we were guided away from a room full of pictures of naked children. At Banksky in Bristol recently, our guide ushered us past the plastic phallus hidden amongst the exhibits in one glass cabinet, not wanting the twins to spot it.

You’ll have noticed that all these instances involve contemporary art. Why do we think modern images are particularly problematic? I’ve never seen – although you may correct me – a notice up warning children away from the anatomically correct genitals on Michelangelo’s David. When my youngest was just three, I showed him the replica at the V&A and his immediate response was to shout out, ‘Big willie!’ Should I have grabbed the handles on his pushchair and made for the flowers on the 19th century French porcelain vases, steering him away from harm?

Brit Art, Banksky and Walking in the Mind were all great exhibitions for kids. At the Hayward, Yoshimoto Nara’s My Drawing Room became a wonderful Wendy house for them to peep into; Thomas Hirschhorn’s tunnels made of cardboard boxes and packing tape were a joy to explore. But at all of them, there were some works of art I was uncomfortable exposing my children to. At the Hayward, Mark Manders’ cat cut in half disturbed the twins. ‘I think that’s why it isn’t suitable for children,’ whispered one of them, guessing completely incorrectly what they were not supposed to see.

I don’t advocate getting rid of all warnings. But I do believe it would be far braver for galleries to own up to who wrote them. ‘We – the Hayward, or even a named curator – believe this work is unsuitable for children.’ It’s chickening out to imply an impersonal authority – Government? The Authorities? God? - has deemed us bad parents if we let our seven-year-old stroll past a picture of a penis.

But most of all, I wonder if it really is productive to point these things out. Human genitals are far more embarrassing – and confusing to look at - for 16-year-olds than six-year-olds. And violence is far more damaging to both of them. So let’s have no more passive voices on gallery walls. If a museum, gallery or exhibition space feels a need to warn parents, that’s fine. But say who is doing it. And, perhaps, why.

More details of TextWorkshop writing workshops for museum and gallery professionals at www.textworkshop.co.uk

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