If you are using the new Google Forms for quizzes and have it set to allow only response, but then find yourself needing to let a student take the quiz again you can work some form magic to do it. It will delete the student’s original response, but if you’re ok with that follow these directions.
From Forms itself:
Click on responses.
Choose the student’s name under who has responded.
Then hit the trash button. This will delete the student’s response from the form and the form will allow them to do it again.
You can also do this in the Google Sheet associated with your your Form.
In Forms click on responses.
Click on the green cross icon to open up the sheet.
If it asks, tell it you want to create a new sheet. (If you’ve already done this it won’t ask.)
In the sheet, right click on the number next to the row of the student who you want to be able to re-take the test. Choose “delete row”. Now the student will be able to re-take it because the sheet no longer sees their name.
Now the student will be able to re-submit the form!