I cut and pack fruit, but it is usually the first thing returned. Maybe it gets warm or there is not enough time. Have you changed the type, packing method or timing and seen a difference?
Our reliable tiffin rule is dry, familiar and easy to eat quickly. Anything that needs careful spooning usually comes back on busy school days. Our child reacted better once we explained the change in advance instead of announcing it on the day. Packing smaller portions reduced the amount coming back untouched. We made the change gradually rather than all at once.
Interesting — we had assumed the opposite. Helpful to hear a first-hand experience. For individual nutrition concerns we still checked with our child's doctor. We are in Bengaluru, so local logistics may be a little different.
If there are concerns about growth, allergies or nutrition, I would discuss the individual situation with your paediatrician/dietitian rather than copy another child's diet. We changed our approach after about a month because the first plan was too hard to sustain. The school lunch-time limit was part of the problem for us. We are in Visakhapatnam, so local logistics may be a little different.