Carol Ness at the San Francisco Chronicle has written a great overview of where the current scientific studies fall on the nutritional quality of organic food compared to conventional, and the myriad of other factors that affect the nutritional content of the produce on your table. The article, Food Conscious: Is organic better? It depends, is not about schools, but it certainly ties in to debates about what constitutes healthy food--the goal for school lunches.
(Found via the excellent local and sustainable food issues website: The Ethicurean)