The basis of the scientific method is to discover by doing. Scientists suggest a hypothesis and then subject it to experimental tests. Over time, knowledge is acquired.
Many people would believe this to be the best method by which schoolchildren can acquire scientific knowledge. The thrill of discovery should be more effective, in theory, than being told about something. And practical lessons have the added benefit of being "fun".
Now, let's stand back and have a think about that.
What do children find fascinating about science? Well, there's the dinosaurs and why they died out. There's space and whether aliens exist. There are questions about why the sky is blue and whether global warming will end the world. None of these topics lend themselves to direct investigation in a school laboratory; a practical lesson is not going to cut it.
And what do scientific experiments that are relevant look like? People often call for relevance without specifying what they really mean, so, by relevancy, I am talking about topics that connect to everyday life, to the lived experience of pupils. Perhaps we could ask them to investigate which brand of paper towel absorbs the most water. Clearly, this would be relevant to the experience of most students because they would be aware of paper towels and what they are for. But it is hard to imagine that such an investigation would fire the imagination. It could be pretty dull.
So, it seems that a sensible approach would be to harness the best of both worlds, focusing on investigating phenomena experimentally but setting aside a little time to discuss and explore the bigger, more philosophical questions. But, unfortunately, this would not make for a good scientific education.
Children need some degree of knowledge to come up with a hypothesis that is worth testing; we should not assume that all knowledge can be learned via the investigation itself. For instance, a good working knowledge of Newton's laws would transform the way a child views and interprets an investigation of motion. And yet, given that very clever people such as Aristotle never discovered Newton's laws, we cannot expect children to work them out for themselves. We need to teach them.
Moreover, the scientific method is something that expert scientists use. Children in a classroom are not expert. They do not possess well-developed scientific knowledge that they can deploy to interpret results. Indeed, they may be in possession of substantial misconceptions. The fact that we tend to relate new knowledge to what we already know - or think we know - means that such misapprehensions can persist throughout a phase of investigative work, regardless of outcomes.
Indeed, such views can be extremely resilient, so they need to be directly and unambiguously challenged. After all, professional scientists spend an awful lot of time analysing each others' work to check for misinterpretations.
We aren't scientists
This is a problem that Paul Kirschner, a Dutch professor of educational psychology, has considered. For him, enquiry-based learning in science can fall down on this very issue. "The origin of these approaches lies in a failure to distinguish between learning and doing; in overlooking that students are not experts practising something, but rather novices learning about something," he says. "It is the teacher's job to teach science, teach about science, and teach how to do science. It is not the teacher's job to practise science as part of the teaching exercise; leave that to the scientists."
Another issue is that once practical work begins, it becomes difficult to focus on the science. "Where are the clamp-stands?" "What should I do with the acid?" "What should I write in the results table?" These questions tend to dominate the classroom when a practical experiment is under way. In focusing on "how" to do the practical work, students run out of mental space for thinking about "why" they are doing it.
Does this mean that we should do away with practical work? Not at all. Rather, investigative work in science lessons needs to be a critical part of a battery of approaches - so long as its pedagogical limitations are recognised.
Crucially, teachers need to directly teach key subject knowledge and challenge children's misconceptions. That way, pupils' experience of investigative work will be much more fruitful.
Greg Ashman is a teacher at Ballarat Clarendon College in Victoria, Australia
Kirschner, Paul A (2009), Epistemology or Pedagogy, That is the Question. bit.lyPKirschner
Kirschner, Paul A (1992), "Epistemology, practical work and academic skills in science education", Science amp; Education, 13: 273-299