Federal School Nutrition Program Regulations
USDA regulations are located in Chapter 7 of the Code of Federal Regulations (7CFR). 

School Nutrition Program Regulations

 School Nutrition Programs
Procurement Regs. for Public Schools Part 3016 - Procurement Regulations for Child Nutrition Programs in Public Schools
Purchasing requirements are found at Part 3016.36(b) through (i) and Part 3016.60 (b) through (c).
Financial Mgt. Regs. for Private Schools Part 3019 - Procurement Regulations for Child Nutrition Programs in Private Schools
Purchasing requirements are found at Part 3019.40 through 3019.48.
Cost Principles OMB Circular A-87 - Cost Principles for State, Local and Tribal Governments