The English chef and TV cook did a whole series "Jamie's School Dinners" where he went into a school and changed the food from what was essentially fast food take away to  freshly prepared healthy food.  There was an improvement in concentration, a dramatic fall-off in children needing to take asthma inhalers during the day and an improvement in results and behaviour. The experiment was so successful it was rolled out to all the London Borough's schools (Greenwich) This was part of a campaign he has to improve school meals which has its own web site  In the occasional diary he writes he mentions visiting the USA.