As children prepare to return to school, the U.S. Department of Agriculture’s (USDA) Food Safety and Inspection Service (FSIS) has developed a food safety “science experiment” that parents and children can carry out together to make sure school lunches are safe to eat come lunchtime.

Children are at high risk of contracting foodborne illness because their immune systems are still developing. In fact, children under the age of five have the highest incidence of Campylobacter, E. coli, and Salmonella infection among any other age group in the United States. This highlights the importance of following the USDA’s four food safety steps whenever preparing meals: Clean, Separate, Cook and Chill, according to the USDA.

The experiment involves testing food temperatures of prepared lunch for the duration comparable to normal lunch packing until consumption. Cold items should still be below 40°F and hot items should be above 140°F. It is considered a “Danger Zone” when lunch food items are found between 40°F and 140°F.

For lunch packing tips and food safety questions, visit FoodSafety.gov.