Many people have tried to figure out ways to save on their grocery bill while still providing good solid nutrition and for some families milk is not even an option or is in short supply. While we don’t drink a lot of milk now, not like when my girls were younger, we still use it for cereal, cooking and baking as well as my daughter still enjoys a glass of milk or cup of hot chocolate from time to time.
One thing we do, and have done for years, is to "cut" our milk. I buy whole milk and I literally dilute it with filtered water. On part milk to one part water. My girls have always preferred this to skim, 1% or even 2% and so do I. It has a much better flavor and texture with half the sugar and calories of whole milk.
It stores well too. I will buy a half gallon, pour off have of that into a couple quart jars to make the diluted milk, then fill up the half gallon with filtered water leaving a couple inches of head space for expansion. After giving it a good shake it is ready for the freezer. You can do this with a gallon too. You literally are doubling your milk and paying half the price per gallon.
So if money is tight, or even if it isn't, this is a great solution to affordably provide plenty of milk for your family. A cup of milk is considered a serving and since most children, especially teenagers, will drink more than one cup at a time I don't think there is any worry of them not getting enough nutrients plus you are also able to get them to drink more water and consume less sugar. That's a bonus right there.