Head
Leader
The neck of the squad is the most important part of the squad, for if you lose the neck you lose the head (they're all one thing). This person is the head or leader of a group.
しゅはん
This is a jukugo word so it uses the on'yomi readings, which you've learned already. Go you!
どいつが新入生の首班を占めることになると思う？
Who do you think will be the leader of the first-year students?