I applied into SSOE for graduate school, so my experience may differ. Before I had a formal acceptance letter I had various professors reach out to me about working in their research labs. When I agreed on one (which happened about mid-March) he had the school write the formal acceptance letter and graduate financial package which was mailed and emailed to me IIRC. But like I said, different schools may do it in different ways. If you’re curious about your status, I would contact admissions.