How can a Team Admin remove players from their team?

A Team Admin can remove players from their team by checking the box next to the player's entry on the Player List selecting “Remove Selected Player” from the “Action” dropdown menu. 

Removing a player from your team removes your ability to manage that player and your visibility into that player's activity. As long as they maintain possession of the Booster, it does not otherwise impact that player's basic Sqord membership. They're simply no longer a member of your team.