Hi @kescobo!
At the moment I’m afraid Classroom only supports a flow where the default branch is called master, but GitHub as a whole is moving away from this pattern, and aiming to let people have whatever default branch name they like for all features and workflows.
We should be making some announcements about this, along with tooling and documentation to make these changes, in the next month or so.
You might want to keep an eye on the Education Community for updates on this particular feature!