Just buy milk without the growth hormones. The carton will say so.
Organic or not, there are milks that have no growth hormones. My local dairy, non organic, has milk like that on the store shelves and I believe there is also one from Costco without growth hormones.
The endocrine system is very complicated in kids... and even BPA's in plastics affect the endocrine system etc. and who knows what else in our environment. And even soy milk, affects the endocrine system in boys/girls and adults.
But yes, kids nowadays are reaching "puberty" early onset puberty sooner... than when I was a kid for example.
Also something interesting, is that a Pediatric Endocrinologist we know, said that the kids nowadays are also watching/viewing, regularly, "teenager" shows, that are not age appropriate for them. ie: even Kinder girls are watching Hannah Montana for example and may have the clothing and posters at home. He said, that these things all can possibly affect, the child/girl. Of course there is no proof or empirical data to say that conclusively and it is a whole issue of what kids are exposed to, from babyhood... and how it affects their development or physical development. But that yes, kids are definitely having early onset puberty nowadays. And, even the things parents use can affect a kids endocrine system. For example: there was a case of two siblings, who started having symptoms of early onset puberty... hair growth in genital areas and armpits etc. After doing an evaluation of the habits at home... it was found that the hair cream their Dad was using for hair-growth (because he was balding), was affecting his kids and being absorbed into their skin as well... affecting testosterone levels etc.
So, milk without growth hormones, is one piece of the whole pie.
Just go to your store, and check out the milk shelves... there are milks, non-organic which also are hormone free.
Anyway, just some rambling about the subject,
All the best,
Susan