In my personal life, I do a bit of volunteering. One of the programs I volunteer with is aimed at public schools. The goal is to convince public schools and districts to take on a micro-farming program, and dedicate adequate resources to it. It can be quite difficult, as people don't really understand the benefits, but every time we get this program established in a new school, six months later, the parents and the teachers and the kids are amazed at the difference in behaviour, diets and attitudes towards food. A couple of schools in the program are even working with one another to specialize in crops, which they trade with one another, so that they can grow more and offset their food costs even more.
In a nut shell, this is the program: every school buys and builds a greenhouse, and creates a community garden. This garden is used to provide fresh vegetables all year round. The students are directly responsible for planting, maintaining and caring for the plants. Each grade is typically responsible for various aspects of the garden, with the responsibilities becoming more demanding and skill-intensive the older they get. For instance, when it comes to harvest time, the little ones will go out and pick the vegetables. Whereas the older grades will be researching nutritional requirements, mixing up organic additives, setting temperatures, and fixing equipment, all year round. People who are interested more in cooking than in farming are put into special groups which make meals out of the produce, and work with the school to develop nutritious meal plans. To keep things interesting, and make the students well-rounded, students are shifted among various responsibilities throughout the year.
The impact has been incredible. Kids who had trouble paying attention are doing much better, because they are getting real food with the nutrients they need, rather than processed junk that is high in sodium and sugar and everything else. Kids with weight problems are seeing a drastic decrease, because they are being taught how to make healthy food that actually tastes good. Even kids who are violent and disruptive see some benefit - not only because they weren't getting what they need nutritionally at home, but because it is a socialization process, and it requires alot of hard work and physical activity - this tends to make kids behave better because they aren't simply cooped up in a classroom, but instead are being active without any sense of competition.
There are other benefits as well - this teaches work ethic and a sense of responsibility and community. Even the most skeptical kid doesn't like it when the plants they are responsible for die. Obviously there are always going to be kids who get no benefit out of this whatsoever, but that is true of school in general, and they are the exception rather than the rule.
This concept needs to be implemented nation-wide, in my opinion. We could even fund it through donations - it really doesn't cost that much once you have the greenhouses built. And the impact would be much larger than simply providing cheap produce to kids. Educational outcomes will improve, which makes them more competitive for the workplace. Doing better economically will reduce crime and violence. And teaching people to eat vegetables will reduce their meat consumption, which will decrease heart attacks, address climate change, and more. It is a small change that would have broad effects.
Take a look at this WHO article about nutritional programs:
http://www.who.int/bulletin/volumes/87/1/08-059519/en/