We do NOT recommend that you recycle old Google Classroom classes with new students. This will lead to problems with any website that is linked to your classroom's old students. Instead, we recommend you use Google Classroom's COPY feature to make a copy of your old class. This will allow you to copy all of the work created in a class, but you can change the class roster of students in this copied class. For instruction from Google Classroom on how to do this, click here: https://support.google.com/edu/classroom/answer/9093680?hl=en
Once you have created your new class using Google Classroom's copy feature and added new students, you will need to import this new class to CommonLit. Do this from the Manage Classes page by clicking Create a New Class > Import Class(es) from Google Classroom.
In Google Classroom, CommonLit assignments from your previous class will appear as drafts with no scheduled date. However, when you copy your Google Classroom class and import the copy, we do not automatically recreate any of these assignments in CommonLit (We wish we could! It's just not possible right now). Therefore, you should not publish any of these draft assignments. You can use these draft assignments as a template for what assignments to recreate in CommonLit and post to Google Classroom, but you will need to delete these drafts from Google Classroom, as their assignment links will not work for students in your new class.