It's not quite a rabbit out of a hat, but when Peter Harwood produces a thin, rubber-tipped, ruler-length metal strip from his big red plastic science box, the effect on Beechwood Primary's Year 5 is magic.
"Who can tell me what happens when you twang the twanger?" he asks these children from Knowsley's burnt-out, litter-strewn Stockbridge estate. Hands are going up all over the place, and pupils are ready with responses: "Sir, when you twang the twanger it goes up and down and it wafts air"; "Sir, you can feel the air moving when you put your hand close to the twanger"; "Sir, when you twang the twanger on the table, the table vibrates."
There are more transformations than party tricks going on at Beechwood, where last year's national test results - for children who are almost all on free school meals - showed 50 per cent gaining level 4 in science and all but one of the rest of the class (45 per cent) gaining level 5, way above the national norm. But as well as performing well in tests, pupils have a passion for science.
"Which is better for feeling the vibrations? - the table or the air?" asks Mr Harwood. An explanation comes from a fragile-looking child on a lower-ability table: "Sir, you can't feel it through the air but you can feel it through the table because the table hasn't got air in it." Others follow: "Sir, in the air it can't, like, get to any vibrations"; "Sir, you can feel it because it goes through the holes in the table."
None of these is necessarily a right answer, and Peter Harwood doesn't say it is. But he doesn't say they are wrong either. "I'm not looking for right answers," he tells one eager-to-please little girl. "I'm just looking for answers."
Later, he says that the previous week one of his pupils had "one of those eureka moments". He adds: "It's not necessarily the brightest kids who come up with the discoveries - but when these kids tell you something brilliant, they're on fire."
Ultimately, any answer won't do for Peter Harwood, who is not only a former head of secondary science (at St Chad's in Runcorn) but also joint author of an A2 chemistry course. His job, he says, is to give the children so much evidence that eventually they have no choice but to come up with scientific answers. To do so, he needs to make sure they come up with as many answers as poss-ible along the way.
This style of teaching science is one he and colleagues at Liverpool John Moores University have evolved over the past five years, during which time he has been working towards a PhD as well as on a project funded by pharmaceuticals giant Astra Zeneca to raise science standards in primary schools.
He says that going round primary school science lessons at the start of his research, what he saw was pupils being taught facts, often without understanding, and quite often by teachers who were unconfident of their own scientific understanding. What children and teachers needed was to be clear about their misunderstandings in order to move on.
To enable teachers to do that, he boiled down the Qualifications and Curriculum Authority's primary science scheme of work to a list of key concepts for each topic (see box). Sometimes those concepts include extra science. For example, he argues that you cannot understand "sound transfer" or "dissolving" without a grasp of simplified particle theory; nor can you explain the effect of forces without knowing about the existence of momentum. Neither of these topics appears in the national curriculum until the secondary years.
He argues that once teachers have grasped these concepts, they see - if they ask their class enough questions - exactly how children's ideas about the world conflict with scientific understanding. Then they can produce activities which make a scientific explanation irresistible. For example, if the teacher understands conservation of mass, then they will believe that a dish of melted ice will stay the same weight as it unfreezes. Not only does that seem obvious, says Mr Harwood, but unfortunately for common sense it is also untrue.
"What actually happens when you weigh the ice using an electronic balance is that it gets heavier by 0.1 gram every 10 minutes," he explains. "The children can see the weight change, so they know something is going on. The first time I did this in front of a class, you could see the teacher thinking, 'Oh no, the weight should stay the same.'
"What's happens is that you get condensation on the ice, and now when I do that experiment I put a lid over the ice and take it round so everyone can see it. Once a teacher has seen that happen, they're more involved in the science. It's more meaningful to them and they feel more confident."
A big part of this approach is making sure that children can actually see scientific phenomena - hence the visibly vibrating twangers. "An important concept for children to grasp is that things are happening which you can't always see, so you have to find ways of showing that they are happening," he says. "You have to convince the children and the teachers that the air is vibrating."
One big question is whether schools can take on this style of teaching themselves once a mentor like Harwood has left.
The Astra Zeneca project has ended now, but Beechwood is retaining him as a freelance science teacher for 10 mornings a year. Some staff there have begun to adopt his style in their own science teaching, says head Christine Taylor, but he is too exciting to lose.
Certainly, there is plenty of excitement in Beechwood's Year 5. After a quick twanging recap, Mr Harwood has sent pairs of children off with mini-tuning forks and little bowls of water to see what they can find out.
Andy Hogg, an NQT who has only just begun working with him, says: "I was amazed at the way he lets the kids run away and explore. He doesn't say, 'You must find this out, you must find that out - they're left to their own devices.' " Over 45 minutes, children come up with experiments to show that bigger tuning forks make lower sounds than small ones; that sound can be transferred from a tuning fork through tables and plastic rulers; that bigger tuning forks make a bigger splash; that tuning forks strung together on thread will transfer vibrations to each other, but when held individually will not; that a vibrating turning fork makes your palm go "buzzy"; and that a plastic cup over the ear will make a very loud amplifier.
During the lesson, Mr Harwood moves from table to table and endlessly questions pupils. What happened? Why do you think it happened? What else do you know about sound that could help you explain it? What words could you use to describe it?
This last is a serious problem in a school such as Beechwood. Despite providing vocabulary lists - bigger, smaller, vibrate, friction - children struggle to find the words needed for coherent explanations.
They can draw diagrams which show they have completely understood particle distribution in solids, liquids and gases, but they just can't put it into words.
Given the pressures of national tests on the school (English results last year were 46 per cent at level 4, 14 per cent at level 5), it is understandable that here, as in others among the 25 deprived primaries in which Mr Harwood has worked on the project, you sometimes find that the closer children are to a teacher or learning support assistant, the more likely they are to be writing instead of experimenting.
But Mr Harwood's evidence suggests that this is a mistake - because his extraordinary success at level 5 in science has been replicated across all those 25 schools, and analysis of these children's national test papers shows that they are picking up all their marks - 50 per cent beyond the national average - on questions that require a real scientific understanding to answer them. "When children get something that Peter is explaining, they really do get it," says Beechwood's science co-ordinator Mike Marray. "There's nothing parrot fashion about what they learn from him - it's based on a real understanding, because they have had to work it out for themselves."
Particle arrangement in solids, liquids and gases
* "Energy in" makes the particles move more rapidly, so further apart; "Energy out" reverses this
* Dissolving means the crystal particles spread out. Evaporating causes the crystal particles to join up again
* Mass stays the same if the particles are trapped. Mass decreases if particles can escape
* Non-reversible changes produce new materials
* Sound is produced and transmitted through vibrations
* Sound travels better through solids and liquids than gases
* Higher pitch is produced by faster vibrations (tighter strings, shorter bars, shorter air columns)
* Dark is the absence of light, blocking light causes shadows
* Light comes from a source and is reflected from or passes through materials which are transparent, translucent or opaque
* We see by light reflecting from surfaces into our eyes.
For a full list of these concepts and sample activities, see Peter Harwood's website: www.pjhscience.co.uk