In the navegation block, under de current course participants there is a link called "notes" that is loading the site notes recorder for all the students in our moodle and not just the site notes of the current course.
In our case, this link take more than 2 minutes in loading because we have many students with site notes recorded by other teachers.
I'm not sure, but I think it is a privacy problem as a teacher can see notes from students they haven't in their courses.
Anybody could confirm me if this is the expected behaviour.
I can reproduce it in moodle 2.9 and moodle 2.6.
It's not a bug... Site Notes can be seen by all teachers in all courses. See https://docs.moodle.org/29/en/Notes#Note_context
If you only want teachers within a course to see notes about students in that course, they need to be Course Notes.