No, I didn't and that was the problem. Thank you for your quick reaction Mary.
Now I have the next problem. I have related a parent user to his 'child user' and I have added the mentees block on the start page of the parent. the parent sees the name of the child in that block. when I click on that user and I go to grades report. the report is empty but i have graded that account on an assignment in a course. I have double checked the permissions of that role.
do you know what I am doing wrong this time?