I emailed schools pre-interview and post to check my status. All were very helpful and told me the information I was looking for. I emailed the school that I was wait-listed at to see if there was a chance I'd be moved off the list, they forwarded my email on to the admissions director to look over my file. But I didn't contact to help out my application, just to check my status. My advice is it's fine to inquire about your application, but don't become a pest about it.