The default is that users have access to User Report and Overview report
But in some courses they can choose among all reports, also reports students don't have access to in the first place.
In the course admin the student has access to Gradebook Setup. When that is choosen all reports are shown, also reports the student has no access to.
I cannot find any place to control the students access to reports in each course.
It seems to me that there is a bug here in the course paramter setting. At least I have no idea on how to access these course parameter setting.