How to get out of a classroom
Since Duolingo's announcement about teachers being able to change your password, several people (who are in "unofficial" classrooms run by their friends, strangers, or just simply someone other than an official teacher) are wondering how to get out of their classrooms. Just go to Settings, then Progress sharing aka remove yourself from the class!. Scroll down and click the big red button that says "Remove". (You might need to follow up by clicking a green button up at the top that says "Save")
If someone who is running the unofficial class you're in has changed your password without your permission, please email firstname.lastname@example.org. Then, try signing out, going to the home page and clicking "forgot my password" It will send you an email where you can reset your password. AS quickly as possible, click my link up above in order to remove yourself from that class.
Whenever you email Abuse@duolingo.com, please provide them with as much information as possible. Give them your email address, give them your username on Duolingo. If you know who is running the unofficial classroom, give Duolingo their username and if you have it, their email address as well.