Elementary school children regularly involved in gardening, cooking and nutrition education are more likely to develop a taste for fresh fruits and vegetables–even leafy greens–and will more eagerly help make fresh meals at home, but those gains come to a screeching halt as kids get older and move into middle school, where they often backslide.

Those are the mixed results of a three-year evaluation of the “School Lunch Initiative” undertaken by Alice Waters’ Chez Panisse Foundation in Berkeley, Calif., schools. Performed by researchers from the University of California at Berkeley, and easily the most ambitious examination to date of an integrated school garden and cooking program, the report [PDF] found that fifth-graders in the second year of the program increased their vegetable consumption by one serving per day and also ate more fruit. Sixty percent of the parents of those children said involvement in the gardening and cooking initiative had made their child more aware of healthier food choices.

By seventh grade, however, student improvement even in Berkeley’s most advanced middle school slowed almost to a standstill, although students were significantly more likely to enjoy the food served in the cafeteria and had better knowledge of how their food choices affected the environment. Still, their small rate of improvement was much better than in schools where the initiative was less robust. There, seventh graders actually showed declines in food knowledge: 6 percent lower in one middle school, 14 percent in another.

The findings roughly confirm my own anecdotal experiences working in the “dining commons” at Berkeley’s Martin Luther King Jr. Middle School where the students, despite being involved in Waters’ flagship “Edible Schoolyard” gardening and cooking program, displayed a conspicuous indifference to vegetables in the food line. The three-year evaluation seems to indicate that while children at a certain age embrace the idea of eating more healthfully, they lapse into a sort of food funk after entering puberty.

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So, do memories of gardening and cooking lessons revive in high school or after adolescence and produce more food-conscious adults? That seemed to be the hope of Berkeley’s food service team, who stressed to me repeatedly while I was there that kids must be exposed to healthier foods even if they don’t eat them, that the lessons will inform their eating habits later in life.

“I think in Middle School developmentally kids are all over the place.  It is really a tough stage and it is also reflected in their food choices,” Bonnie Christenson, executive chef for Berkeley schools, said today when asked about the evaluation’s results. “In high school you see the kids starting to eat salad again. They are moving away from their parents’ control but they are more mature and responsible. They eat a wider variety of foods including veggies.”

But, as Christenson notes, “The study doesn’t cover a long enough period to reflect this.”

“I really do think it makes an impact for life–truly,” said chef Ann Cooper, who was hired by Waters to reform the meal program at Berkeley and now runs food service for schools in Boulder, Co. “Middle School is tough no matter what. But in all other academic domains we continue to work with them and we need to in this area as well.”

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Waters, who was quoted celebrating the study’s results in the Washington Post and the San Francisco Chronicle, did not respond to my query about the underwhelming middle school results.

Berkeley schools are in the fifth year of a major food service overhaul instigated by parents with help from the Chez Panisse Foundation and the non-profit Center for Ecoliteracy. The schools eliminated processed, reheated meals and adopted food made from scratch. A local bond initiative helped pay for a new central kitchen. Meanwhile, the School Lunch Initiative, designed to show children the connection between how food is grown and prepared and their own health, installed gardens in all 11 of the district’s elementary schools and three middle schools. Thirteen instructional kitchens were built.

Waters’ vision of children growing and cooking their own food has inspired school gardens across the country. The perceived benefits have been the subject of sometimes furious debate.

To varying degrees, students in Berkeley’s “School Lunch Initiative” were engaged in gardening and cooking intermittently during the school year, but the program was stronger at some schools than others. For instance, some schools did not have paid garden staff or dedicated cooking instructors. Over the course of the three-year evaluation, researchers used questionnaires as well as photographs of what kids chose for lunch to measure the impact at schools with the most highly developed programs, compared to those where kids spent less time gardening and cooking.

In the more dynamic programs, for instance, food grown in the garden was harvested and used in a cooking class. The same food was then served in the school cafeteria. The Martin Luther King Middle School, where Waters’ original “Edible Schoolyard” is staffed by several workers in the garden, and includes a lavish kitchen facility with individual work stations, a convection oven, a dishwashing area, and a dedicated instructor, was not mentioned by name in the report. But the best results seventh graders managed to muster out of the district’s three middle schools–presumably at Martin Luther King–was a five percent improvement in food knowledge, despite all the resources lavished on them.

Initially, 327 students were involved in the study, but by year three the number had dropped to 238.

The Berkeley schools are racially and ethnically highly diverse. Among all the families involved, more than 90 percent of parents said it was “very important” to serve their child fresh fruits and vegetables every day, 75 percent said it was important to serve whole grains, and nearly half thought it was very important to serve locally grown foods.

Researchers said they were puzzled that overall only 30 percent of the children studied helped with meal preparation at home.