Non-organic milk is FILLED with extra growth hormones, antibiotics, and pesticides (from what the cows eat), and the way they treat their cows is awful. Organic milk is free from these things... The tests they have done in people that have ingested regular milk have shown great evidence in those growth hormones and antibiotics going straight into our bodies.
Back in the old days, "regular" milk didn't give all their cows those toxic things. (So I don't wanna hear the argument "I had regular milk and I'm fine") In fact, it is funny that "regular" milk is called so. Organic milk is technically "regular" milk and "regular" milk is acquired in a VERY non-regular way: mistreating cows and pumping them with hormones and antibiotics.
My thing is, if I can choose to NOT have my children ingest all that extra stuff I don't want in their bodies, then I will chose organic. Most things we buy are organic... but , honestly I think choosing organic milk out of it all, is the most important. We still have some non-organic things... but I'm just happy that I am GREATLY reducing the amounts of pesticides, GMO's, growth hormones, antibiotics( which actually has contributed to infections that are immune to anti-biotics, I believe the body is SO used to them), and other toxins that are not regulated.
My FAV, though? Organic whole goat's milk! YUM!!! it is also easier on the tummy!