You can only have one active lesson at a time, but remember students can still work on lessons that have ended by going to their Study history tab.
If you want to run more than one EF Class lesson at the same time you can with Assignments! Start an Assignment for Class A and pick the activities you want to send. Repeat the same for Class B. The lessons will be available in the Study history section of the student app.
Still need help? Our support team can help you get the most out of EF Class. Email us at email@example.com.