Think all organic products are made to the same standards? Sadly this is not the case. Not even with dairy, which seems like it would be fairly easy to regulate. Fortunately, I found a great resource, Cornucopia Institute, that maintains a rating site for organic milk and dairy items. I'm sure it's not perfect, they are, after all, out to protect family farmers, but it's hard to argue with the methodology of measuring operations to "true" organic intentions.
If you're in Central PA, where I am, your best options are: Organic Valley or Wegmans' organic milk and Stonyfield yogurt. These all rate a "4" on a scale where "5" is highest. The worst choices, rated as "0" on the scale, include: Horizon, Organic Cow and Aurora Organic. Nature's Promise (Giant), Kirkland Signature (Costco), BJ's and Archer Farms (Target) are also all scraping bottom with a "1" rating.
If you are closer to Philly, try to get dairy from one of the small farms with a "5" rating in Phoenixville and Oxford. Find them on the ratings chart.
What brands do you buy? I am very loyal to Organic Valley, partially because they also have a Lactose-Free 1% variety that sits well with Gregory. If they are sold out, I will buy Stonyfield (which scores a solid "3"). For yogurt, I buy Stonyfield most of the time. I've found that the quarts are the best deal and they keep pretty well once opened.