What separates 'mid' from 'low' tier? Do you mean how selective they are? If that's the question, look at the current residents, where they did medical school, that sort of thing. But I wouldn't any conclusions on how 'good' the program is based on those things. I'd look at the board pass rate, read the description of what the program is like and ask here whether anyone has rotated there. Most programs are very good, meaning that you will get a great education in general pediatrics and will probably be able to get a fellowship afterward. It's more whether the program fits what you want.
