To check your Course Request setup, navigate to:

Academics > Schedules > Requests and Schedules > Course Request Setup
Select the School Year from the dropdown
Towards the top, you will see a Header for: Exceptions To Communicate there are the following options:
  • Has already taken the course
  • Lacks prerequisite
  • Assigned to a different grade level than the course
You can select the following choices within the above options:
Show message to display a message to the Student (Note: Students can still request for Has already taken the course and Assigned to a different grade level than the course even when set to show message the System allows them to confirm and select)
Hide course from list to hide requests from the Student
Ignore to Ignore and not communicate to the Student