The program piloted in 2018 in 15 Brooklyn schools. New York City Mayor Bill de Blasio announced on Monday that the plans would expand to include all 1.1 million students in city public schools by the fall of 2019.

“Meatless Monday is great,” Amy Shapiro, a parent and registered dietician, told the station. “When we take out the meat component we can focus more on the grains and vegetables and we put vitamins and nutrients in they might not be getting otherwise.”

A statement from de Blasio quoted the mayor as saying, “Cutting back on meat a little will improve New Yorkers’ health and reduce greenhouse gas emissions.” Meat production creates significant greenhouse gas emissions.

Meatless Mondays is one of the programs of the Monday Campaigns, a non-profit initiative from Johns Hopkins, Columbia, and Syracuse universities. School systems in Baltimore, Los Angeles, and Philadelphia are some of the larger ones that have already adopted the policy, according to the organization. The term comes from its original use during World War I, when the government urged families to give up meat and other staples to support the war effort.

Some critics say that while lowering meat consumption can be good for health, it depends on what is substituted for it. A grilled cheese sandwich, for example, may have almost as much saturated fat as meat.