This is going to sound very old-fashioned. Still, I'm used to having to defend my favourite lesson to parents who don't realise just how many of the government's desirable learning outcomes can be learnt through simple sand and water.
I wouldn't knock computers and CD-roms, which we have, but basic sand and water can be presented in many different ways. It can be solitary or group, and children love it.
Science, pre-maths, language, creativity, even music: sand and water can help with the lot. Dry sand can be sifted and used for weighing. Children see its substance change as you add water and learn that it weighs more and can hold a shape. You can add food dye and talk about how the sand changes colour.
It's very good for experiments: will it sift wet or just dry? They see how things change. Which things float and sink? Which things take in water and which don't?
Language comes into it because you're talking about what's happening to the sand and the children are expressing their feelings about it.
You give them some wet sand and say: "Now does this feel any different?" There can be a lot of adult interaction. We talk about where sand comes from and where you would find it.
And of course - rather underrated these days - it's good for their creativity. We have sand on the floor sometimes and let them imagine where they might be. Sometimes it's a beach and they talk about their holidays. Or maybe dinosaurs live there? Perhaps it's a building site with cars and a cement mixer? Sometimes they will just trace patterns in the sand.
It's good for number work, weight and volume. We have weighing scales, and of course we're always filling containers and asking things such as: "How many spades does it take to fill this bucket?" With sand and water you can ask "Now what would happen if . . . ?" We fill milk bottles with sand or water. Then we say: "Tap it. Does it make a different noise? Does the noise vary according to how much you put in?" They just really enjoy it. I've yet to find a child too sophisticated for sand and water. I feel sorry for groups that don't provide them - perhaps because of hall rules.
So when parents concerned about desirable outcomes and the national curriculum say to a child whom they're picking up: "Oh, is that all you've done? Just messed around with sand and water?" I have a lot to tell them.
Pauline Thomas is leader of Lloyd Park under fives centre, Walthamstow, east London. Run by parents for two-and-a-half to five-year-olds, it opens from 8am to 6pm , and has an afternoon drop-in centre for toddlers