What makes a good lemon-juicer? Ease of use? Looks? Price? Safety? The amount of juice it squeezes out? This was just one of the problems facing teachers at Design Into Practice, a workshop run by Gillian Shaw, education officer at London’s Design Museum as part of a national programme of training funded by the Design Council. Having tested four designs and given them marks on a scale of “pips”, we decided a simple perspex dish was the best. A flashy metal lever-operated press came bottom.

The workshop was part of an Inset training day for Kent schools held at Southborough Primary School in Tunbridge Wells. Ms Shaw is holding similar workshops all over England, prompted by the Office for Standards in Education’s concern that design technology is often neglected in schools, especially at key stages 1 and 2. She also runs workshops for children at the museum.

“Many teachers seem to find the subject difficult,” she says. “We aim to give them ideas that are simple and fun, which they can take back to their schools and share with colleagues.”

She began by introducing us to the museum’s mystery loan box - a large multi-coloured chest on wheels that opens up like a giant swivel-top pencil case. Inside are 11 intriguing objects, chosen to encourage pupils to be “design detectives” and work out what they are used for.

Teachers who attend the workshop get the box on free loan for at least two weeks so they can show it to colleagues and use it in class.

First we had to guess what the box was made of. Chipboard? In fact it consisted of layers of recycled washing-up liquid containers, which with their bright colours, made an ideal packaging material.

Then she delved inside. Out came a silvery, pear-shaped cylinder with a pipe through the top. Then a brightly coloured, open-sided plastic tower.

After much discussion the group identified the first as a kettle, designed by Phillippe Starcke, although Ms Shaw explained it was a collector’s item rather than being of practical use, because the combined spouthandle got too hot to hold. The other item was a can crusher that sells successfully at Pounds 59, often to schools that have set up recycling programmes.

“Does an object look good? Does it work well? How could it be improved? These are the key questions children should be encouraged to think about,” she said. Teachers agreed the contents of the box encouraged them to take a fresh perspective on everyday products.

Next came the lemon-juicers - of remarkably varied designs. “What criteria should be used to judge them?” she asked, handing out a supply of fresh lemons to ensure that our survey was fully comprehensive.

The task seemed simple at first but rapidly became more complicated as we discussed how factors as diverse as safety and the separation of pips from juice should be weighted. As well as being fun, it was a vivid reminder of the educational value of group discussion and having to agree on joint conclusions.

Pointing out that design technology extended into other curriculum areas such as maths, science and history, Ms Shaw also asked us to imagine - and draw - the mechanism inside one of the more complicated juicers.

As the training pack given to everyone attending the workshop says: “Pupils should be taught to investigate, disassemble and evaluate simple products and applications, to learn how they function.”

She recommends car-boot sales as an ideal source for building up collections of similar items to study. “Construction kits have a role too, as long as the children aren’t simply playing with them,” she said. “They always need to think about the design of what they are making.”

Ms Shaw had also brought along a collection of cups and beakers, ranging from disposable vessels to a dainty china teacup. Holding up the simplest of all, a plain paper cup, she asked when we thought the design had first been produced and why.

Most of us reckoned it was in the 1950s, to save washing up, so we were surprised to learn the cup was invented in 1912, to reduce the danger of TB being spread from the use of shared cups.

Then the group took it apart, discussing how the lip strengthened the cup and made it easier to use - the perfect design.

Workshops can be booked through Education Department, Design Museum, 28 Shad Thames, London SEl 2YD. Tel: 0171 403 6933. The mystery loan box and five others (on history, telephones, Victorian items, radios and kettles) are also available for hire (Pounds 25 each for two weeks plus transport)