For most children, London's Trafalgar Square is a familiar attraction. In the north-west corner is a plinth that has been without a permanent sculpture for 150 years. The other three plinths have statues that fit 19th-century moulds of self- aggrandisement, including Sir Henry Havelock who got his place among the pigeons for his part in suppressing the Indian Mutiny.
However, in recent years there have been a number of temporary exhibits on the empty fourth plinth, organised by the Fourth Plinth Commissioning Group. Their choices have caused much controversy and debate and, from the tabloids, predictable derision. Marc Quinn, better known for a head sculpted in his own frozen blood, has gained notoriety for his sculpture of Alison Lapper, a pregnant thalidomide victim.
All this helped in setting the scene for a project with my Year 8 and 9 students, the aim of which was to produce an architectural-style drawing of the plinth using two-point perspective, with pupils' sculpture idea convincingly fitted on top. The picture was to be finished in watercolour.
To begin, pupils sourced images and information about the plinth from the internet. The Fourth Plinth Commission has an excellent website and there are also plenty of images available using a search engine. We then discussed the difference between sculptures recently exhibited on the fourth plinth and the more traditional statues on the other plinths. This generated ideas on the nature of sculpture, in particular the use of less traditional materials such as resin, used in Rachael Whiteread's up-ended mirror-image sculpture of the plinth in 2001.
Next we tackled perspective. A few simple exercises worked, first using one-point and then two-point perspective. As the plinth is seen from below, the line of sight is low, with the plinth looming above. Using an image of the empty plinth from the internet helped the class work out the desired perspective. For homework, they drew a cereal box in first one and then two-point perspective.
The final image had to include the National Gallery behind the plinth and St Martin-in-the-Fields in the distance, so the next step was to get them to draw a number of two-point perspective boxes of differing sizes using foreground, middle-ground and background. We discussed whether this was actually the way the world appears to us, using examples from the past, notably Canaletto.
Once the pupils had mastered perspective, it was time to develop the sculptural idea. I have found the most successful to be something quirky and fun. When I first devised the idea the plan was for a sculpture that crossed Surrealism with Pop Art. In particular, it was Meret Oppenheim's 1936 "Luncheon in Fur", that seemed a good starting point, alongside countless products from everyday life that function as one thing, but have the qualities of another, such as my prized 1967 JVC Videosphere - a television in the shape of a space helmet.
I proposed that pupils choose two objects - ideally quite different - and find a successful way of combining them. Neither object had to be functional and there was no restriction on size. Claes Oldenburg, for instance, combines bold colour with oversized objects in his sculptures.
First, we made observational drawings of both objects. Secondary sources such as photos, magazine images or internet sources could be used. These drawings effectively helped produce the shape, form and even texture of their objects.
The next task was to find a way to combine these objects. Pupils had to work on a number of drawings to find the best way. The finished sculpture could be something as direct as upholstering a sofa with rubber tyre tread - or more complex, such as merging two distinct forms into each other at different angles.
The final piece in the puzzle was to understand how objects appear when seen from below. As the Trafalgar Square viewpoint is from below, the top of the plinth obscures the object, which will also appear foreshortened, so that the shape appears squashed. I demonstrated this by showing pupils an image of Nelson on top of his column or the waxwork of David Beckham that appeared on the fourth plinth before the 2002 World Cup.
Once the object was conceived, the pupils produced the two-point perspective of the plinth and surrounding buildings. Having laid out the perspective drawing, they drew their object on top, taking care to foreshorten it. To get the best effect I found it was a good idea to have part of the object hanging off the plinth, although if you do this too much it will look ready to fall off. A shadow completed the illusion of the overhang.
Finally, they added a wash of local colour, a red bus passing behind the plinth and, if they wanted to, further texture and shading using blow pens over the watercolour. To render the object itself, coloured pencils - or a combination of watercolour and pencil - gave most scope for adding plenty of detail. Of course, we could have done the whole thing much quicker using Photoshop, but that's another project.
Donald Short is head of art at Moyles Court School, Ringwood, Hampshire