Moodle allows staff roles to change what different users can or cannot do within a certain activity. The list of capabilities is very long and is unique for each activity and changing permissions can lead to privacy and security issues. Some of the capabilities, with higher risks, are locked and you will not be able to change them.
By default, only lecturers can rate students. If you want students to rate their peers you need to update the Rate posts capability via Permissions for the relevant activity.
Please, contact the Digital Education team via IT Self Service Portal who can change this permission for you.