A Nursery Nurse has a formal qualification - NNEB - which requires at least two years college training and she can run her own nursery, be left in charge of pre-school age children and can supervise non-qualified staff. A nursery assistant usually has no formal qualification, needs to be supervised by trained staff and assists the nursery teacher or nursery nurse in the nursery setting.
Of course, Nursery Nurses can command a considerably higher salary than that of a Nursery Assistant .
Having said that, I have worked with excellent nursery assistants who have been brilliant at their jobs, and with Nursery Nurses whose skill and commitment has left a lot to be desired - so qualifications aren't everything!
Qualified Nursery Teacher.