One state declined a simple tweak to its summer meals program. Thousands of kids paid the price.

There was plenty of food in the orange coolers full of free summer meals when a father pulled up, asking for two suppers to bring home to his children. But staff at the meal site in this rural community, where over 60% of students qualify for free or reduced-price lunches, could not give the man anything. 

That’s because Missouri chose not to opt in to a federal waiver that allows parents and kids to pick up meals and take them home, a pandemic-era benefit that vastly expanded access to meals.

Missouri was...