The number of breakfasts served in the nation's schools has doubled in the last two decades, a surge driven largely by a change in how districts deliver the food.

Instead of providing low-income students free or reduced-price meals in the cafeteria, they're increasingly serving all children in the classroom.

That change has been pushed by food policy advocates who say it increases equity, but it also fueled a backlash from parents and teachers who contend it needlessly takes up class time that should be devoted to learning and wastes food by serving it to kids who don't want or need it.

Since 1994, the number of breakfasts served has climbed from about 1 billion annually to 2.3 billion, according to the U.S. Department of Agriculture.