Very, very, very selective from what I’ve heard. However, you should know that the quality of the applicant pool isn’t as high as a college pool, and ALL(not most) of your app depends on essays. You don’t submit grades or anything.
What I’ve heard is that this year, 400+ people applied, and only 20 of us got in. 5% acceptance rate. But don’t quote me on this because I didn’t get it directly from the source.