Securly On-Call allows admins to assign contacts to different schools, Org. units, and Security Groups to ensure maximum coverage during and after school hours. Some contacts might be assigned to more than one school at any given point in time.
If you want to remove a contact from just one school, you would need to edit the schools assigned to that contact from the "Edit contact" option. For this, navigate to Case management > School contacts and select a school and then click "Edit contact". Here you can add or remove schools assigned to that contact, so you can add or remove the contact from that specific school.
As contacts can be associated with multiple schools, it is recommended that you do not delete the contact completely to remove them from a school, but instead remove the school-contact mapping using the method described above. This would ensure that On-Call coverage for other schools assigned to the contact is not impacted.