I was called the "Team Captain" this year, and that's what we use on letters or stationery sent by me. However, other common names (as you can see from my profile title) are "Student Leader" and "President." Our team constitution stipulated that the election is held for the "Team Captain," which is defined to be identical to "FIRST Student Leader" and "Club President." The multiple names for this position were made in order to:
(1) make sure the 'club' is actually a TEAM (hence "captain")
(2) abide by our school's 'Club' regulations - we must have a President
(3) identify who is designated in the FIRST Team Registration form as Student Leader

This year, all the team's final decisions went through me, the Captain. We also had "Directors" for each group (animation, PR, robot build/design). These Directors (Vincent for PR, David for Animation, and Me for Robot Build/Design) would delegate tasks to their groups and communicate their group's needs to the Captain. We also had a Assistant Captain, William - but this position is only active after our last competition is over and we hold elections for next year's captain (i.e. the Captain-elect for the next year is also the Assistant Captain for the current year). Generally, a Captain is either elected by students or appointed by the mentors, whichever is appropriate for that year, and then remains Captain until s/he graduates. All of these students make up the "Leadership Council." Next year, some students want to keep the Captain final-in-command, others want to increase the power of the Leadership Council, but the Council-elect members seem to be working well together anyway, and the ones who argue about such things aren't on the Council.

But in joking, we also call our various Leadership Council members "general," "comrade," "dictator," "supreme ruler," even the "head Fajita" (but that one's only for me )