The child is out of the parent's control for hours at a time and often has a little money and walks past grocery stores and fast-food restaurants on his way to school. Even if you send him a healthy lunch he may use it for trading at school and eat something entirely different. So, cross your fingers and hope that all the information you gave him earlier will bear fruit. The child is still growing in spurts. Murphy's law says that a growth spurt always occurs two weeks after you buy expensive new shoes.
Breakfast is by far the most important meal.
The brain simply cannot work without fuel. The best way to get a child to eat a good breakfast is to eat one with him. He still needs after school snacks. You need one, too. This is required by law as far as school lunches are concerned.