If I rephrased the OP as “give the half eaten restaurant leftovers to be used as school lunches” people would say that is horrible but somehow OK for homeless people?
I must have phrased it poorly, because I never meant to imply half-eaten food. The idea is to portion it out before the food is brought to the table. ("half of their meal is then portioned out" should have been phrased differently; "first" instead of "then" is a better fit)