As millions of students around the nation return to school cafeterias this month, Congress will begin to make some important decisions about what exactly those students will be eating in the years to come. The “ Child Nutrition Reauthorization ” (CNR) takes place every five years and shapes federal legislation that authorizes and funds the National School Lunch Program and other key child nutrition programs. But the CNR involves more than just pro forma approval of these long-standing programs. It also gives lawmakers an opening to review—and potentially alter—child nutrition policy. In the...