P rogress of any kind always seems to give rise to a whole new set of problems. So you invent the motor car and a hundred years later there is gridlock in our cities. You make cheap electricity available to all, and emissions from power stations cause acid rain in Scandinavia. Or you design a sophisticated modern school, a warm, airy place of sunshine, glass and greenery, where teachers want to work and children want to learn. And the mealy bugs eat all the passion flowers.

“We were devastated,” says Ralph Wylie, principal teacher of biology at Leith Academy in Edinburgh. “They were such a wonderful show. We haven’t been able to build them back up yet, but we will.” Mr Wylie is strolling along a thoroughfare called the “Main Street”, which would be the central corridor in a traditional school, but this corridor is so spectacular it has been featured in the BBC’s Beechgrove Garden. Ahead of him stretches a vista of ferns, flowers and trees dappled with sunlight streaming through the glazed ceiling. Quadrangles planted with cherry trees and shrubs open off the street, as well as classrooms, study centres, the dinner-hall and library resource centre. Benches are placed at intervals among the foliage, and original paintings and reproductions of old masters line the walls.

“These palm trees are not supposed to get below 15 degrees,” says Mr Wylie, “but they will survive in this bed next to the swimming-pool. That plant is monstera. It’s a toughie, loves it here.” He lifts the huge, raggedy leaf and points to a little white patch on its underside. “See that? That’s your mealy bug,” he says, pulling it off and eyeing it with disfavour. “Looks like cotton wool and you’d think there’s nothing there, but it causes a lot of damage.

“We don’t have frost or predators to aid us, so we never totally master the pests. A systemic pesticide would be best but they’re so lethal it would mean closing down the school and bringing in a team of certified contractors. So instead we wipe the plants with soapy water, which the children will tell you is a lot of work.

“That tall plant is a yucca that we were given because it was getting too big. Quite a lot of our plants are given to us but we also have to buy some each year after the winter. Those pink flowers are busy Lizzie, a bedding plant; they’re past their best now. We usually make a small profit from the bedding plants.

“This is magnolia, and that’s a marvellous avocado grown from a pip and now it’s way above our heads - we’re hoping to get fruit from it some day. This is bougainvillea, a wonderful show with its beautiful pink leaves.”

But looking attractive and smelling sweet are rarely enough to justify your existence - you must also work hard. Leith Academy’s plants are no exception.

“We use them as a resource in biology. We study chlorophyll and where starch is produced in variegated leaves. We look at stomata opening and closing. We bring the classes out here and study the relationship between the insects that feed on the sap and the ants that tend them. We do experiments on woodlice - there are different species with different preferences. We study the vine weevils with their four different stages of life. And of course we learn all about the mealy bugs.

“Art is also a big user - a class will come out here and be drawing, sketching and painting among the plants. And geography - they have a weather station in one of the quadrangles and they use our cacti.”

Upkeep of the Street is co-ordinated by Mr Wylie, who is allocated one period a week for the purpose, but pupils, teachers, technicians and janitors all help out, and a contractor is employed for a few hours a fortnight. A manual sprinkler system and soaker hose have been installed to help with the watering.

“Plants have a very calming influence,” Mr Wylie says, “but I do worry about them if we have four or five hot days in a row, and during the summer break I sometimes pop in to school to make sure they’re all right.”

Leith Academy has a tradition dating back to the 16th century, but the unique building it now occupies was constructed in 1991. Headteacher Sandy McAulay says: “The architect Laura Stevenson got the teachers involved in the design when she was drawing up the plans for the building. So it’s a fantastic place to work; there’s a real feel-good factor. You won’t see any graffiti, and the children respect the plants and look after them. They are proud of their school.”

Each spring pound;300-400 is spent replenishing flower beds and pound;285 per quarter is paid to a contractor to come in every fortnight for a few hours. A small profit is made on the bedding plants.