hamza443
Yes, you are right, you can only drop a student which is enrolled in a course.
If you need the "delete" button back, you will have first to remove all the objects (courses, grades, attendance, discipline referrals, etc.) linked to those students.
For a course (its grades and attendance), this would mean selecting a drop / end date anterior to the start date. You will be asked if you also want to delete grades and attendance.