Calcium and phosphorous are two minerals necessary for healthy bone development. Milk has both in spades, plus it's fortified with vitamin D in the United States. Not only that, but milk is stocked with protein, energy fueling carbohydrates, Vitamin A and magnesium, another beneficial-to-your-bones mineral. Full fat milk is OK for kids up to two years of age, then take it down to reduced fat milk. Most kids like the taste of milk because of its association with cookies and cereal, so you can use this to your advantage to get milk into their system. The popular ad slogan says it all -- milk does the body good.