Assemble a mini photo album stocked with pics of the people and things your pipsqueak misses most during the day: Mom and Dad, brothers and sisters, his Lego set, his dog. Then ask his teacher to let him leaf through it when separation anxiety strikes. While it sounds counterintuitive (won't that just remind him of all the reasons he has to be sad?), seeing all those familiar faces can comfort a kid who's missing Mom and remind him that he'll get to see his favourite people at the end of the day.