There's no official rankings for Osteo schools. However, in the US News list, they rank osteos in with allopathics. If I remember correctly, MSU-COM and WVU-COM made it in the top 50 for primary care? Someone jump in and correct me.
However, you have to take these all with a grain of salt. There's a lot of factors that determine which med school is right for you.
I advise you visit the schools you're interested in, and talk with as many students as you can. There are plenty of students from any school here on SDN who are willing to share their opinions.