Can I start or asisgn more than one session at a time?

Yes, you can choose to host and/or play multiple sessions simultaneously.

You can also have multiple session types — live or homework, running at the same time. Each session comes with its own report, and you can view the progress by going to the Reports tab. 

You needn't open multiple browser tabs to run additional sessions. Once a join code is generated and players join the game on their device, the session and its progress will automatically appear under Reports.