Having taken part 1, I can tell you from experience that the boards are an individual sport so to speak. Every dental school will offer the same basic science classes with the same emphisis. It all comes down to how well you want to do and how much you are willing to sacrafice to do it. In a thread a few months back students replied with how well they did, how much time they studied and what they studied. You'll see a pattern emerge. Schools have higher scores due to simply having more students who want to specialize and will study harder to get those higher scores. If you want to do well, you can go to Harvard or a State school and you'll get roughly the same score. No school offers a class that gives their students any edge.
The only differences between schools that could impact your score IMO are the amount of time off the school gives you to study without classes or clinic.
I'll give one more exception. Schools that don't rank students also tend to have higher averages. This is because everything in the world rides on those students' scores.