"My students can't see their quiz scores!" "Why can they see their attempt and all the questions? I just want them to see their score!"
The quiz Review Options, found on the quiz's Settings tab, is the key to controlling these issues and more. Here's a video explanation, followed by some instructions below:
Review options can be found by clicking on the quiz link from your course page. Then click Settings in the menu along the top. On the Quiz settings page, expand the Review options section to display the following matrix and select what information Students will be shown from the quiz when they review their past attempts and during the attempt if you use adaptive mode. Some settings may be disabled depending on other settings for the quiz. For example, if your quiz doesn't not have a close date/time, "After the quiz is closed" options are inoperative.
Typically, instructors will set the review options to allow students to see the points after completion of the quiz, but not the Right answer. This prevents possible sharing of the correct answers before the quiz is closed, but allows students to see the score on their attempt.
To see the on-screen descriptions in the settings, click on the blue question mark icon 
beside each under the During the attempt.
Definitions
During the attempt - What the students can see when they are taking the quiz. These option are inoperable when How questions behave has been set to Deferred feedback in the quiz settings (the most common and popular setting). When otherwise enabled, the quiz includes a Check button with each question; when students click Check, their answer is locked in and whatever review items are set for this group are displayed (which may be none, which may then confuse students). When the Check button is not clicked for a question it is reported at the end of the quiz (when Finish Attempt is clicked) as Not complete; however, when Submit all and finish is clicked all answers are submitted whether Check was clicked or not.
Immediately after the attempt - Means that, after the student clicks Submit all and finish on their quiz attempt, the selected review items are available to them for 2 minutes.
Later, while the quiz is still open - Means that, after the student submits, but before the Close the quiz date/time, the selected review items remain available if no close date is set, or until the Close the quiz date/time is reached.
After the quiz is closed - Means that, the selected review items are available after the quiz is closed, and can no longer be attempted. These options are inoperable for quizzes without a Close the quiz date/time set.
- The attempt: Whether the student can view their attempt at all. That is, can they see the actual questions on the quiz. When deselected, only options available are Points and Overall feedback.
- Whether correct: Whether the student's response to each question is correct or incorrect.
- Points: The score awarded to the student and the grade for the quiz. This will show the overall score for their attempt.
- Specific feedback: Feedback for the response to the answer selected/entered by the student. Each question can have feedback for both correct and incorrect answers. These must be set up for the question in order to be displayed in the review.
- General feedback: Feedback for the question regardless of student's answer. Use general feedback when creating the question to give students some background to the knowledge covered.
- Right answer: The correct answer to each question, whether the student answered correctly or not (see notes below). Basically, this "releases the key."
- Overall feedback: Feedback for the entire quiz as set in the Quiz settings.
Tips!
Consider what options you select and how much you will reveal the quiz to the student. For example, you might allow students to see their quiz results immediately after taking it but not later when they might share it with others. To do this, make sure none of the boxes under Later and After the quiz are checked.
It is also helpful as an instructor to "think through" the testing scenario as the student would experience it given your specific quiz strategy. For example, say you allow 3 attempts on a quiz and you set it up to retain the highest of the three grades. If you do not show the student their score ("Points" in the Review options) after their attempt, how will they know if the need to or wish to try again?