They certainly know their onions when it comes to growing vegetables but pupils from one school were left close to tears after a sneak thief raided their allotment.

The cabbage patch criminal made off with 30 onions and a dozen shallots that had been carefully cultivated by pupils at one of the region's smallest schools, Bishopstone Primary near Swindon.

The budding gardeners had hoped to show their produce at today's annual Bishopstone Gardening Society Show and yesterday made a final plea for the culprit to bring back their onions.

They have even made a series of wanted posters in the hope of regaining their prized veg in time for the big show but fear the evidence may already have been consumed.

It is the latest, and the meanest, in a series of allotment thefts which have been blamed on the credit crunch, with people are stealing produce to save money at the checkouts.

Yesterday head teacher Sue Walton said: "The children were close to tears when they discovered the theft. They were disgruntled and angry. One of them commented that it was irresponsible.

"You teach the children about morals and right and wrong and then something like this happens. We were flabbergasted really. You don't expect it, not in a village like Bishopstone.

"They put a lot of work and enthusiasm into it. The children's parents were indignant. They all said they couldn't believe it.

"We've only had the allotment at the school for two years and this would have been the first time they had entered the village show."

The youngsters had proudly unearthed their veg before laying it out to dry when most of the produce was swiped.

Mrs Walton added: "The most exciting thing about growing vegetables is getting the produce out of the ground and the children were very pleased at the results."

Curiously, the raiders left the leeks and some other produce so at least they will have something to show at this afternoon's event.

Yesterday youngsters spoke of their anger and dismay.

Nine-year-old Molly Barratt said: "The people who did it should give them back because if they enter them into the show, we will find out."

Charlotte Cunnington, 10, said: "We worked really hard to make the onions and then someone took them without permission." And ten-year-old Ryan Sutton added: "The thief should own up before he eats them."

Gardener Adrian Dent, who helped pupils grow the veg and who they know as Top Turnip, said: "It was a wonderful crop and the children would have won a prize at the show. I think it was an inside job as whoever did this knows their onions."

Some of the pupils' posters show weeping onions, while another depicts an adventurous vegetable heading into the distance with a rucksack on its back.

It follows a series of garden raids in recent weeks that prompted one allotment committee at Ottery St Mary in Devon to launch evening patrols. Committee chairmen, Adrian Foster, who has had raspberries, peas and runner beans stolen from his allotment, said he had never experienced such high levels of thefts in the 22 years he had been there.

He said: "In times gone by, we occasionally had thefts of produce or equipment but it was negligible."

Torpoint Allotment Association in Cornwall has also introduced night time patrols to deter thieves.