As an educator on Canva, you automatically have a classroom created when you set up your account. This can be the classroom you use for all of your classes, or you can create multiple classrooms to better sort your students. As per the Canva help page:
"How you set up your class is up to you. You can use one class per school, per grade, per subject, or per class that you teach."
Read more on creating and managing your classrooms on Canva here.