By default, Grades are not shown to students. It is possible to change this so that each student can see his/her own grades. The settings to do this are not in the Grades tool, but rather in the Course administration settings. These settings can be accessed by clicking Edit settings either in the Settings button in the upper right corner of the main page, or in the Administration block on the right side of the page, below Message my teacher. Note that it is not possible for students to see any grades other than their own.

On the Edit course settings page, scroll down to the Appearance settings. The third entry is Show gradebook to students. Change this to Yes.

To complete the change, click Save and display at the bottom of the page.

Note that students may not know where to look for their grades. You can show them how to do this by showing or telling them about the Grades selection from the Profile dropdown menu in the upper right corner of the page.