How do you handle students who drag down their team?
As the dynamics between students change, you should see teams auto-regulate themselves and students help each other be well-behaved. It's often a good idea to put troublesome students on teams with stronger, more extroverted students so that they can balance each other out from the beginning.
The teacher can also intervene should the problem continue. You can remove the student from their team and put them alone (in unassigned players). With a little luck, they'll quickly see that being alone isn’t great and will want to come back to their team.
Tip: Make sure to have students sign the Hero Pact so playing is their decision. It's normal to have a couple students who choose not to play. This may change over time, and regardless, they'll still gain the benefits of the overall improved classroom atmosphere.