Sales of organic milk have boomed in the last few years as consumer opt for a more natural option to pour on their cereal, but according to the Cornucopia Institute, an organization which works to protect the integrity of organic farmers, not all organic milk is equal.

The organization recently produced an organic milk scorecard, enabling consumers to see which brands and dairy products are produced using the best organic farming practices and ethics. Based on a year’s research into the organic dairy business, the scorecard rates 68 different organic dairy brands and private-label products, and while it found that 90% of organic farmers stick to the rules, a minority doesn’t.

Factory farms, which own thousands of cows rather than just a few hundred like many organic milk producers, come under particular criticism. The Aurora Dairy Corporation, for instance, which owns five dairy facilities in Texas and Colorado and provides milk that is sold as organic to some of the nation’s biggest chains, including Wal-Mart, Target, Costco, Safeway and Wild Oats, is accused of breaching the laws of organic production.

Cornucopia’s research, since confirmed by a two-year investigation by federal law enforcement agents, found that Aurora was confining their cows to pens and sheds in feedlots rather than grazing the animals as the federal law requires.

An independent study by the United States Department of Agriculture (USDA), which grants organic certificates, also concluded that the Aurora Dairy “labeled and represented milk as organically produced, when such milk was not produced and handled in accordance with the National Organic Program regulations.” Despite these findings the USDA have yet to take any action against Aurora.

To protect their business and the reputation of organic milk, however, organic dairy farmers across the country have filed a class action law suit against Aurora. The suits charge Aurora Dairy Corporation with allegations of consumer fraud, negligence, and unjust enrichment concerning the sale of organic milk by the company.

Until the conclusion of the lawsuit, however, consumers can still check just how organic their brand of milk is by using the online Cornucopia scorecard.