In the end it really doesnt matter what school you go to, so long as you have the accreditation to write USMLE/MCC exams. Some of the older schools give 2-3 months to prepare for step1, while newer ones can be more 'generous' in offering a few more months to prepare for your boards. This would have to be taken up with the Dean of Academics of the school.

There are no issues with residency. Only issue for licensure is with the states that require their own approval for each school (ex. california, etc).

With ASUM, you have to write step1 after basic sciences, before you can do your clinicals.

For the board exams, its upto you on how well you prepare yourself. Not based on what school you go to. A school may help you motivate yourself in some ways for the boards, but in the end you are all that is to be accounted for. All you have to do is study.

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-Food for thought. Facts to quench the thirst.