To prevent students from seeing their scores right after they submit an auto-graded quiz, please follow the steps below.
1. Access the Submission Views tab in the Quizzes tool (this is the section where you set up what students will see immediately after they submit their quiz. Please visit this post for more details).
2. Select Default View to edit what they will see by default.
3. Uncheck Show attempt score and overall attempt score in the Score section.
4. Save the view and save the quiz before navigating away from it.
