Note: You may refer previous revisions for more context.
I read Academia varies more than you think it does, but in any school or university I've been to or heard of, students can always see how they were graded for any assignment. Or, at least, if the school won't let them keep it, but they will at least let the students view it (usually final exams).
I believe it's every student's right to know how e was graded on, well, a graded requirement. (see Dan Fox and David Hill's answers) The only exception I can think of is Educational Testing Service, which administers the TOEFL and GRE, but it's not really a school or anything.
Recently, my sibling was a little surprised with a grade on a paper and wants to know about how their particular paper was graded. But when my sibling tried to ask to view the marking of the paper, this was the reply:
Are you an exchange student? [University] does not provide marks to students after the examination. The only thing that can be released is the Grade or Pass/Fail. Giving you the marks would be a violation of the regulations. In fact, all such information will be destroyed after a period of time. You can try asking other teachers about marks, they will also tell you the same.
(My sibling is not an exchange student.)
Some guide questions for the main question:
Is this policy unconventional or unethical or unfair? Based on Corvus' answer to this question or Dan Fox's answer to this question, I kind of think my sibling's university's policy is unconventional or something.
How will any student get feedback on their communication or their mistakes if they do not see any of the marking of their work?
Is it unconventional, unethical or unfair to tell them to ask other teachers rather than point to the specific university regulations?
Is it unconventional, unethical or unfair to not have specific university regulations on this matter?