You can choose which groups to sync with Math Games by using the Edmodo sync dialog.
Note: Your Edmodo students will need to have their access set to "student" in the Edmodo dashboard to be available to sync.
Learn more about this here: https://support.edmodo.com/hc/en-us/articles/205005494-Turn-off-Read-Only-for-an-Entire-Group-Teacher-
To sync your Edmodo groups with Math Games.
1. Navigate to the classes tab
2. Click the "sync with edmodo" link
3. Choose which groups you would like to sync and click the "sync" button
4. You classes and students will now be displayed in your Math Games dashboard