Not sure why "..when we log in with a teacher account we cannot even
view the certificate." Are there conditions where you can see the
certificate? Or after creating the certificate, it is not showing up
on your list of available certificates? Can teachers see a standard certificate that is awarded to a user in a student role?
Assume you are playing around with customizing the certificate files.
I am a little rusty but here are some ideas. Users can have more than one role and/or you can change roles for specific users in specific activities. What about creating an activity that is graded by a master teacher. The grade could be the number of students in the teacher's group. Set the condition for the teacher's certificate to get more than 1 in the activity. If you are clever enough to insert the number of people in the group the teacher manages, don't display the grade field but the group count field.
I am looking at upgrading Moodle from 2.2 to 2.9 so have returned here after a long absence.
Hope this helps - Chris