thanks for your fast reply,
but yes I had ensured multiple times that I just followed the instructions in Parent role,
and the parents aren't enrolled in these courses, also these courses doesn't have guest access...
but although parents can see different type of reports for different courses,
the normal case is that parents can see only Activity reports(Grade) but in some courses which their children are enrolled in it they can see Activity reports(Today's logs, All logs, Outline report, Complete report,Grade).
is this is a bug in moodle 2.8 or this is related to the type of activities per course?
I mean some activities in the course generate other reports?