When I was growing up in NYC in the early 1960's, we were very poor. I qualified for free school lunches at my public school. I was thrilled to get the canned peas, instant mashed potatoes, franks&beans, canned peaches, Salisbury 'steak', milk, sometimes an apple. Sure there was a high proportion of canned and processed food, but often it was my only meal for the day, and it was usually was the only fruit and vegetables I had access to. i ate every molecule, plus the stuff the other kids were going to toss away. It tasted wonderful to me because I was actually hungry.
When my own children went to public school, I was horrified to see giant vending machines selling Coke, candy bars, and potato chip in the hallways, and frozen pizza offered as the main lunch item.