Clearly, food choice and consumption is related to how much is wated on school trays.
Source: NetOf course, Wansink is not alone, and other scientists have entered into the sensory studies and food waste arena – in particular, Erminio Monteleone of the University of Florence. Monteleone heads the European Sensory Sciences Association and is a favorite consultant for organizations such as Slow Food. Often partnering with Caterina Dinnella and others, he shows what has happened to the decline of the structure of the classical Italian meal – from a primo, and secondo (a pasta and fish dish, for example) 
to “single-plate” meals – but with less waste. In terms of tray waste in Italian schools, he feels this is an important direction to be moving in, children prefer this “new innovation.”[1]
Source: plate images, net. More typical single-plate Italian meal.
One very important aspect of Wansink’s work is the role of emotions in food consumption. If you’re in a lousy mood, you just may eat more (B 19).[2] People eat raisins when happy but M+Ms and buttered popcorn (i.e., hedonic or “happy, comfort” foods foods) when sad (Study: Am Marketing Association) 
[here] And so we sometimes overeat to manage moods – and what are people overeating? Now this overeating of comfort foods, at least in some clinical trials, was interesting: (189, B 22, B 25). People preferred potato chips, then ice cream, then cookies, then candy.