A lot of schools do this, when I applied I had several schools not give me any sort of status update until June when that rejection letter finally came or the wait list never panned out.
If the interview period is over and you haven't received an interview, you're out.
If you've interviewed and the class has filled and you haven't heard anything, you're out.
If you've interviewed and it's been a long time and the class is still not full, sit tight, you're just not one of the top applicants so they've kept pushing your file to the next round.