I was tempted in to see Harry Potter and the Deathly Hallows: Part 1 by the trailer, which promised something horrific and disturbing and yet still targeted at children -- a combination that always intrigues me.

If a filmmaker is happy to get an 18-rating (or "R" in the US), there are naturally far fewer limits on what can be shown. Aiming instead for a family audience imposes obstacles around which a skilful director will relish manoeuvring, often creating in the process a more intimately chilling work. With the button marked "explicit" placed out of reach when you can't go any higher than a PG or 12A, some ingenuity is called for. I like seeing how filmmakers work around that.

I didn't get the chance with the latest Harry Potter because all the spooky bits showcased in the trailer have evidently been saved for Deathly Hallows: Part 2, which opens next summer. That said, the new picture does have one moment that will give any teenager the heebie-jeebies; it's a kind of Solaris Junior episode in which Ron (Rupert Grint) is taunted by the manifestation of his worst fear -- Hermione (Emma Watson) smooching with his best friend, Harry (Daniel Radcliffe).

The series has had its occasional frights, usually revolving around the soul-sucking Dementors. But scaring children is an important business. Someone should put some proper work into it. I'm sure Disney's crack at a live-action ghost story for kids, the 1980 film The Watcher in the Woods [2], looks creaky now, but it spooked me and my friends as 9-year-olds. (It also provided my first encounter with Bette Davis, long before I saw All About Eve. Funny how we stumble accidentally upon those we will eventually love.) We were all careful to count the number of times The Watcher in the Woods made us jump; by the end, we had almost run out of fingers.

Can children still get those feelings from movies now? Or have video games filled that void? I suspect it's the latter, although the only empirical evidence I have to go on is a recent conversation in which my 16-year-old son passed on to his 10-year-old sister advice on surviving a zombie attack at school. How proud I was.

Two recent animated movies, Coraline and Monster House, pushed their young audiences as near to outright horror as it is possible to go. In fact, one of the writers of the latter, Dan Harmon, believed that Monster House went too far; you can read his brilliantly frank letter [3] to a young girl who'd been terrified by the picture, in which he explains how the script was rewritten, and how its director Gil Kenan ("a hack") and producer Steven Spielberg ("a moron") made it oppressively dark against Harmon's wishes. It's odd thinking of Spielberg having anything to do with that decision, when Jurassic Park and The Lost World were fatally compromised by their need to mollify the audience they were supposed to be frightening.

Last year, Guillermo del Toro signed a deal [4] with Disney to develop and produce a series of scary films for children, under the new Disney Double Dare You brand. Sadly nothing came of it, and the latest [5] word from del Toro is that DDDY is no more. I hope the idea is revived in some form or another; children like, and need, to be scared, within reason, and it's not a bad idea to have a series of films dedicated to doing the job properly.

I showed my eldest daughter Tim Burton's Pee Wee's Big Adventure when she was four or five, and she was properly spooked by the sight of Large Marge [6], the pop-eyed, stop-motion ghoul with whom Pee-Wee Herman hitches a ride. Once she had recovered from the shock, she asked immediately to see it again. I know that feeling.

I must have been more disappointed than I'd realised by the lack of chills in Deathly Hallows: Part 1, because as soon as I got home I started watching Stop! Look! Listen! [7], the BFI's new two-disc volume of archive films from the Central Office of Information. This is the fourth such volume and it contains some absolute blood-curdlers. Everyone knows there's nothing scarier than public information films, especially those made in the 1970s, when the gritty urgency of cinema and television seemed to licence in them a new toughness and daring.

Stop! Look! Listen! contains a pair of mini-masterpieces of the form. One is "Apaches", a 29-minute short by John Mackenzie (who later made The Long Good Friday); its warnings about the dangers of playing on, with or around farmyard machinery stayed with me into adulthood. I only need to see a combine harvester in repose and I get a chill.

But the film which got to me as a nipper, and still freaks me out now, is "Never Go With Strangers", directed by Sarah Erulkar. (Other work by the Indian-born director is screening [8] at the BFI Southbank this Thursday.) As I watched it again this week, it was like revisiting the scene of a partially repressed childhood trauma; instantly I was transported back to the mustard-carpeted "television area" of my Essex primary school, where we were all herded to watch this stark warning of the dangers of skipping off to see a strange man's puppy/goldfish/newborn donkey.

Erulkar's short has an economical but striking visual power. Images from the film are seared on my brain -- like the child whimpering in the shadow of her unseen kidnapper, or the sudden imposition of demonic eyes on the face of an apparently innocuous face as the narrator says, "If a man looked awful, if his face changed when he was doing something bad, it would be so easy not to go with him." (That gimmick didn't have quite the same kick when it was wheeled out for the "New Labour, New Danger" poster campaign [9].) And there are details I had forgotten, or never noticed. As the shadow looms over the child, and the voiceover says "He's big, he's frightening, he can be rude and nasty, and she can't do anything about it," we can see debris all around her, including one especially disturbing detail -- a doll with its head snapped off.

What saves the short from overkill is its essential sanity. It addresses its young audience in a reasonable, sophisticated voice -- one from which modern governments might learn a great deal when raising with the electorate the subject of terrorism. The film reminds viewers that most people wish them no harm. And it respects their independence too: "You're not babies any more," the narrator says. "You want to be free and find a bit of adventure." Any shortcomings can be blamed only on semantics or naivety. It is unfortunate that the script differentiates between people who are kind to children and those who are "unhappy, lonely, peculiar or bad", adjectives which I'm sure could apply to most of us on drab days. There's also the comforting but unhelpful illusion, still upheld today, that any threat will come predominantly from outside the family, when we know this not to be the case.

The COI Collection: Stop! Look! Listen is available now. Harry Potter and the Deathly Hallows: Part 1 is released on 19 November.