Open-ended was once a buzz-word. Primary teaching had to be open-ended, and so did children’s learning. It spooked people. Positive, successful open-ended practice resulted in new learning - for both the teacher and the children.

Now it appears that open-endedness rides again. The Government’s strategy for primary schools, for instance, encourages us to be creative across the curriculum.

But a lot of well-meaning open-ended primary science education came to grief on the twin rocks of children’s inexperience and teachers’ limited subject knowledge. Besides, “open-ended” had an arty-farty, sloppy-thinking, sandals-and-finger-painting kind of image. How could it possibly relate to a structured, organised, clear boundaries kind of subject like science? Great brains weighed in and pointed out that, when you blurred subject boundaries, you mixed more than metaphors - a lot of language is subject-specific.

Open-ended science suffered from unpredictable practical problems too. A carefully structured study into what brought the seagulls down on our London playground straight after play nose-dived when the gulls went back to the sea. Open-endedness was rather like buying shares in Marks Spencer. It should have been rock solid, but all too often it meant high-risk, poor returns.

And yet, when it is well-planned and structured, an open-ended science activity can be a triumph. I remember arriving for one six-hour practical (science undergraduates have always had a heavy timetable) to be presented with a lab full of equipment, including an X-Ray machine and a lead-lined apron, and a tank full of rather anxious-looking frogs.

Our demonstrator (then a penniless PhD student, later to head the country’s leading marine biology research station) asked us simply: “How can frogs jump so far?”

After some time spent finding out quite how far, and side bets on some Olympic champions, we began to focus on leg length. Then came some hints:

“What do you know about levers?” Examining frog skeletons and x-raying frogs in squatting and full-stretch positions led us to the conclusion that the frog’s leg - including its pelvis - made a lever of extravagant length - and that a good kick-off with a lever that long could take a frog a very long way.

Nobody is suggesting that you X-ray frogs with the foundation class; but there are questions you can usefully ask that will stimulate original thinking. Let’s qualify that. The chances of Jatinder or Jason in Year 4 devising a totally new piece of science are pretty slim - but the probability that they will discover something that is new to them is remarkably high. Creativity in science in this case is described in the Association for Science Education’s Primary Science Review as “the bringing together of existing ideas, information or evidence in original ways to generate new entities or ideas”. And if that’s not an explanation of real, insightful learning, then I don’t know what is.

The challenge for teachers is to identify the right questions. With that in mind, the Qualifications and Curriculum Authority website National Curriculum in Action is really helpful. It defines the characteristics of creativity (and I paraphrase here) as behaving imaginatively and purposefully to produce something original of real value.

For that to happen, children need space; but unlike the old practice of open-endedness, this space should be defined - and indeed, circumscribed.

And we can set them to work in this way because we have a pretty fair idea of where they may end up. It’s a little like setting off on a journey with a sketch map - as opposed to the comprehensive Ordnance Survey map that is the national curriculum. We know roughly where we are going, but it won’t surprise us to arrive somewhere different.

This often happens when I set familiar science challenges - keep the water warm as long as possible, dissolve the jelly cube as fast as you can, grow the best cress, keep your paper spinner in the air the longest.

Groups and individuals will assure me that yellow cups stay warmer longer; that black jelly cubes dissolve fastest; that cress by the window or the radiator grows best or that bigger paper spinners take longer to fall. And the temptation is to say: “Oh, I expect that’s because ...” But then you miss out on the best bit. That only comes when you say: “Why do you think that is?”

One schoolboy, later to be a Nobel prize winner, was greeted each night on his return from school by his mother. Instead of asking what he did in school today, she would ask: “Did you ask a good question?”

Good questions in science lead to creative thinking.

John Stringer is a primary science consultant and head of education for The Future is Wild.Primary Science Review 81, Association for Science Education, JanFeb 2004, is a special edition on Creativity and Science Education. www.ncaction.org.ukcreativity is the QCA creativity website.Challenges in Primary Science by David Coates and Helen Wilson, David Fulton Publications, pound;15, is full of good questions to ask in and around KS2 science; both practical ideas and discussion starters.www.thefutureiswild.com is a scientifically accurate but imaginative look at the future which stimulates the creation of new habitats and creatures