what school? There could be a couple reasons. the first (and more optimistic one) is that they haven't made decisions yet. Many schools take 2-4 weeks to send them out. Hopefully this is the case for you, but each school is different. Another reason could be that they have offered initial acceptances and you are on the waitlist (some schools don't tell you if you're on the wait-list). If someone declines their position they will offer it to the next person in line and so on till some one accepts.
Im in the same boat as you and while i'm trying to remain hopefull, I'm pretty sure i'm in the second group. If i don't hear back from anywhere by the end of spring break im going to apply to a couple masters programs with late deadlines that have faculty with similar research interest(as a backup) and hope i get a notification from the schools im waitlisted at before April 15th