Why does it look like a student is still in a quiz that has already closed?
If the quiz is closed, then your student no longer has access to it. However, they may not have submitted their quiz prior to exiting. The following is what an attempt looks like when a student started taking a quiz and got out of it without closing it. If you need to give this student another chance to take the quiz, click in the box beside their name, then click "Delete selected attempts" below the list of attempts. You can use User overrides to set up the new attempt for this student. Contact your Moodle Administrator for assistance.