Can a student retake a quiz sooner, or get credit without one?

Yes. Both are in the student's quiz log.

1. Open the Quizzes tab.
2. In the Students table, click the magnifying glass on the student's row.
3. Click … on the quiz, then choose:
   • Change retake date: pick an earlier day, and the student can retake from then.
   • Admin certify: count the book as read without passing the quiz.
   • Delete quiz: remove the attempt entirely.

Change retake date appears while the student is still waiting to retake. Admin certify and Delete quiz appear for quizzes the student didn't pass. Admin certify also appears on a passed quiz for a book outside the student's ZPD: passing doesn't lift the reduced points for a book below it, but your certification does. Classes still in their free trial can't change retake dates or delete quizzes.

To change the wait for the whole class, go to Settings → Quizzes and click the days in "can retry a failed or abandoned quiz after 14 days" (3–90 days; 14 by default). It counts only for quizzes that end after you change it. A student who is also in another class waits for the longest of their classes' settings, so a shorter wait in yours may not shorten theirs (students in more than one class). To shorten a wait that's already running, change that quiz's retake date.