How to set user level permission?

I’m using Education module and trying to give the permission for a document to a student to see only his/her data. For example I’ve given the student doctype permission to a student and if student will login then he/she can see only his data, but right now I’ve logged in as a student and see all other students data also (Showing in the screenshot). So, how can I restrict it to role level.

And I’m getting the option to add student. So, how can I remove this option for student role?

Please give the Role “Student” to students.