Why shouldn't cafeterias offer fast food lunches?

Eating fast food everyday in school can lead to obesity which then leads to health problems. Another reason that cafeterias should not have fast food in lunches is because we all know that the kids will want to eat it, but eat junk food at schools everyday will not help with his or her education. It affects the brain and does not let the kids focus as much. If anything they should change the fast food into more nutritionist and healthier foods.