Do you need your username or password?
Student usernames: Ask your teacher to check their "List of registered students" to find your username.
Students needing passwords who registered themselves: You can reset your password with your username and the answer you provided to the security question when you signed up. Teachers can reset student passwords by clicking "Change student username / password" in the "For teachers links."
Students who got their username and password from their teachers: Ask you teacher to retrieve your username and password.
Teachers: If you need both your username and password, you must first retrieve your username, then use your username to reset your password. In most cases, your username is your school email address.