A CNS (and also a NP) is a type of Masters degree program. Some schools will accept people who have no experience in nursing and some won't. You'd have to talk to the schools that interest you, to see what their philosophies are. I think having experience as an RN will make you much more competent as a CNS. I started my CNS a couple of years after I got my BSN, and did it one course at a time. By the time I graduated, I had lots of experience in several different types of nursing. The experience was SO valuable!!