The Tribune reports on school food illness outbreaks across the United States. The series finds that "dangerous practices exist in the factories where school food is made and in the kitchens and cafeterias where it is warmed and served." The government inspection system for monitoring the $5-billion-per-year school-food business is flawed. It is often difficult to trace spoiled food because subcontractors' identities are rarely disclosed to school officials. The reporter looks at a notorious case in which 1,200 children in North Dakota were sickened by contaminated tortillas.