I have been making school lunches for my kids for most of the school year and only recently started getting clear feedback. The daunting task of figuring out what from the fridge or pantry will satisfy and nourish my kids is no easy task. As is common in most kids, they are picky eaters based on texture, inappropriate color (apples turning brown), or smell. There is no guarantee what something will end up like after several hours in a lunch box. Additionally, our kids have food allergies so we are further limited in food choices and there is NO sharing or alternate options at school. Some days the kids would be famished by the time dinner rolled around and probably persuaded us to provide mid-day snacks.
My wife would often clean out the lunch boxes. She or the kids would occasionally mention to me what they did or did not like. It wasn’t until I cleaned out the lunch boxes myself did I really see what worked and didn’t explicitly. Then I would ask the kids what they liked or didn’t and why. The conversations and the evidence of the lunch box was enough to create a full feedback loop so I could make changes in the future. Needless to say, improvements were then made.
UPDATE: I also started showing them what their lunch was going to look like in the morning. That way I could get feedback beforehand and make changes as required. Also, I am setting expectations of what is to come so they build their interest for lunch. Nothing wrong with some surprises though from time to time.