To remove a class, you can archive it. Here's how:
Choose the class you want to archive > Settings
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You will see a modal window pop up. Select Archive Class

Read the warnings :) All active experiences will immediately end and all data will disappear, and only become accessible through Exploros reporting. 

You also have the option of removing all students in the class from your All Your Other Students list.
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We recommend doing this if you no longer teach the students that were in the class you are archiving.

If you are using the free version of Exploros, your archived class data will disappear, and not be visible for both teachers and students. If you have an Exploros subscription, either directly with Exploros or through an Exploros publishing partner, you can view archived class data. 

Read this article for more information on viewing archived class data.