To be honest, every director I've worked with so far in educational theatre has had a different idea on what exactly a stage manager's duties are, so what I would suggest is to ask your director if you could schedule a time to sit down and talk. Once you've done this, tell the director openly and honestly that you aren't really sure of everything that falls under your responsibility and that you'd like to go over what he/she would like you to take care of. Always ask questions if you aren't sure of something, a director or designer might seem to be slightly annoyed if you ask a question they consider to basic, but they would be considerably MORE than annoyed if something went wrong because you didn't have that answer.