Answer:
Pizza is sometimes referred to as a vegetable when it is served in school cafeterias because it is typically made with tomato sauce, which is considered to be a vegetable under U.S. Department of Agriculture (USDA) guidelines. In 2011, the USDA issued a guidance to schools that allowed them to count tomato paste as a vegetable serving, regardless of the proportion of tomato paste used in a given recipe. As a result, pizza with tomato sauce, which typically has a small amount of tomato paste, was counted as a serving of vegetables. This guidance was intended to make it easier for schools to meet the USDA's requirements for fruits and vegetables in school meals.