Pasteurization of milk heats the milk to a specific temperature and then cools it down. This process kills harmful bacteria. If the milk is then stored properly (40 degrees or less), it is dramatically less likely to pass dangerous bacteria to someone drinking the milk.
Milk sold in stores and breast milk from milk banks is pasteurized. What is called "raw milk" is not pasteurized. Raw milk does not have proven benefits AND it is NOT safe: the bacteria that are in raw milk are dangerous. Although raw milk and unpasteurized breast milk is available on some "secondary markets" (such as Craigslist), do not offer it to your children.
I would strongly recommend that raw milk never be consumed by anyone, but children and pregnant women are at most risk. Please see these links at Healthy Children for more information here and also here.