Nothing new really. When I went to public school (elementary) then grades 1-6, the schools in that era all cooked their food fresh and the only thing they really brought in already made was bread and milk.  Fresh  produce and fruits were
supplemented by canned vegetables and fruit and meats, fish etc.
The  food was cooked at each school and most schools had a dietician as the cafeteria manager.  As such, the food was very good.  This all changed by the time, I graduated from high school in the late 1960's.
The food began being made elsewhere and as the quality declined, so did the number of kids who bought school lunch.  The DOE has been chasing its tail ever since.