You might want to select a title that best presents you to the outside world - outside your team. When recruiting, when soliciting sponsorship, when being introduced to other teams, to judges - what title best describes your role on the team?
I like short and sweet - student leader.
From that you can then go on to say what some of your responsibilities include. If you are introducing one of your engineers to someone, you would likely say, this is our lead engineer (or whatever role they fill with the team). If you are introducing your teacher who is also the team leader, you would quite possibly say, this is our teacher. If you were introducing a NEM (non-engineering mentor), you would say, this is one of our mentors. You can lump engineer, teacher, and NEM together under mentor but oftentimes, how you present them conveys who they are and how they contribute to the team. Same thing with student titles. Communication in all forms is best when kept simple, clear, brief.
Edit: This is a post that I found from Kyle Love that says what I'm thinking. Read his last bullet.
http://www.chiefdelphi.com/forums/sh...2&postcount=14