TOO much theatre for adults won't admit that ''let's pretend'' is at the heart of every drama. We get actors making out the audience is not there, directors imagining there's a fourth wall, and playwrights believing they'll curry favour with seriousness alone. Audiences are duped into thinking they're seeing something worthy, not noticing the magic has gone.

Children's theatre never suffers these hang-ups. Actors look their audiences in the eye and ask them to join in, sometimes verbally, often musically, always imaginatively. There's nothing apologetic about their suspension of disbelief, because no-one wants to disbelieve in the first place.

Take the finest moments in Sir Janet and Pyjamas, two plays that opened yesterday at the Scottish International Children's Festival, which plays all week at Edinburgh's Traverse, Royal Lyceum, Theatre Workshop, and elsewhere. Sir Janet is a

brains-versus-brawn piece of storytelling written by Louise Ironside and performed by Wee Stories Theatre Company for five to eight-year-olds. At one point the heroine, played by an unshowy Isabel Wright, finds herself in a dark forest with only the stars for company. In one delightful touch in Andy Cannon's production, the actors ask the cross-legged audience to

create the night sky with a galaxy of twinkling hands. The effect is lovely.

Then in Pyjamas, a very funny bedtime whimsy by Italy's Teatro dell'Angolo, you realise the stretcher being carried to motorway carnage, a collision of vehicles, emergency services, and a helicopter, is actually a bed being dragged over to a pile of shoes and an umbrella. With a puff of talcum and a twist of a shirt, the two performers, Paquale Buonarota and Alessandro Pisci, lay down the rules for the kind of fantasy world in which children need no schooling. Let's pretend? Let's pretend all theatre was like this.