A Repl.it classroom is a collection of assignments with additional autograding functionality. It can be used as a sole learner who wants to practice programming in a specific language, or it can be used by teachers and instructors to deliver programming instructional material to their students.
Currently, classrooms use a different editor than repls. The editor is less-fully featured, but we have plans to upgrade in the future. Classrooms can take advantage of the functionality offered in repls by using Classroom Projects.
Students of a classroom will have a series of assignments to complete. Their dashboard will simply be an ordered list of assignments. Depending on the classroom, subsequent assignments may have prerequisites.
Students cannot see which other students are taking the course, nor can they see any information about their teachers or assignment metadata.
Teachers have a much wider view of the classroom - they have full control over the assignments, including the order in which students see them. They are able to add students and TAs, and can see the entire student roster as well as which assignments each student has completed.
Assignments submitted by students can be manually or automatically graded on a binary scale (complete or not). Teachers can send assignments back to the student with comments, even if the student passed the automatic tests.
No one other than teachers can see student rosters - even if your classroom is public. Note that teachers can also not see who has enrolled in the class as a self-learner, only the number of self-learners.
You can become a student or teacher by going to your account, going to 'roles', and checking the box next to 'student' or 'teacher'. Once you've updated your roles, you should see new navigation links in your header.
You can also become a student or teacher by going to the classroom community and importing a classroom. "Taking and Learning" a classroom will automatically make you a student, while "Importing and Teaching" a classroom will automatically make you a teacher.