Passing rates of USMLE Step I are meaningless in the sense that if you attend a school with a 99% pass rate and you are that 1% that does not pass, you have a problem. As others have said, it's the USMLE Step I score that matters most.
Attending any medical school in this country can provide you with the material that you need to do well on USMLE Step I. It's up to the individual to master the material and rock the exam.
No matter which medical school (in this country) you attend, you can be the person who aces this exam with excellent preparation and mastery of your coursework.