Pack your child's lunch in a insulated lunch box. An insulated lunch box locks in the temperature of its contents to help keep them cool or warm, depending on what is inside. Include a frozen ice pack in the lunch box to help keep items cold. Place the ice pack next to items you want to stay the coldest, such as milk or yogurt.
Pour the milk into a thermos. Similar to a insulated lunch box, a thermos is insulated to keep its contents warm or cold, depending on what is inside. Pour cold milk directly into the thermos and screw on the cover. The milk inside the thermos should stay cool for several hours.
Pack your child's lunch the night before and keep in the refrigerator until he leaves for school. In an insulated lunch box, the contents should stay cool for several hours.
Place heavy lunch items on the bottom of the lunch box and lighter items on top. Items such as thermoses, juice boxes and pudding cups should go on bottom so as to not crush sandwiches or bags of chips.