An admin can control which blocks can be added to course pages

1. Log in as a teacher, go to your course and click the 'Turn editing on' button.
2. Try adding an activities block and a course completion status block to the page.
3. Delete both blocks.
4. Log in as an admin and go to Settings > Site administration > Users > Permissions > Define roles.
5. Edit the teacher role and remove the block/activity_modules:addinstance capability, then click the save changes button at the bottom of the page.
6. Go to the teacher's course and in Settings > Course administration > Users > Permissions, remove the teacher role for the capability block/completionstatus:addinstance.
7. Log in as the teacher again, go to your course and click the 'Turn editing on' button.
8. Check that you are no longer able to add an activities block nor a course completion status block to the page.