Mr Kitchen is the founder of Rocket Gardens, in Cornwall, which ships young plants to primaries all over the country. These can be planted to form an on-site kitchen garden. Alternatively, schools with limited outdoor space can grow plants in pots and window boxes, in classrooms or outside, or on roof terraces.
"We've become detached from the countryside," he said. "Generally, children don't know how a carrot or a tomato grows. Even teachers don't necessarily understand what a runner-bean plant is.
"We're demystifying the process. We show it's not hard to grow your own food."
The seeds are sown and nurtured in Cornwall. Schools contact Rocket Gardens with details of their pupil numbers and growing space and Mr Kitchen recommends various plants. The average order comprises about 120 seedlings.
The young plants are provided free of charge: schools pay only pound;30 for postage and packing.
"Growing carrots from seed, it can be difficult to distinguish the plants from the weeds," said Mr Kitchen. "Pupils lose interest.
"We make it simple. You see instant results. Pupils come back after half-term and there's a garden growing."
Rocket Gardens provide print and online teaching packs, to help teachers incorporate their classroom crops into lessons.
And Mr Kitchen hopes that pupils will pick tomatoes from window-boxes or salad leaves from classroom pots, to eat as break time snacks. Once they have tasted home-grown vegetables, he believes, they will be reluctant to return to the supermarket variety.
"We want to catch children early, get them from five years old," he said.
"Why not grow things yourself? We're re-engaging with nature."
Pupils at St Paul's, a primary in Hammersmith, west London, have been growing carrots and onions in boxes in their concrete playground. Michelle Hostrup, the assistant head, believes this has allowed the pupils to examine their attitudes to fresh food.
"Some children didn't know that carrots grow underground and are covered with dirt," she said. "With the Rocket Gardens, the connection between something growing and something you're eating is more immediate. And foods that children might have looked at and said 'Oh, yuck', they're now motivated to pick and eat.
"It's important to give children a sense of where their food comes from.
They can see that you don't have to live in the countryside to grow things."