CORRECT. Even though the person inquiring may be the student's parent, FERPA recognizes students in postsecondary education as adults, regardless of age. Therefore, you cannot give out that grade, or any other non-directory information.
At the postsecondary level, parents have no inherent rights to inspect their son's or daughter's education records. When a student reaches the age of 18 or begins attending a postsecondary institution, regardless of age, FERPA rights transfer from the parent to the student. Therefore, you must assume that the student is entitled to privacy, even from parents. Parents may assert their rights to the records if the student is dependent according to the tax code, but the College is not required to disclose information from the student's education record. At Bucks, we do not release information to parents without the written consent of the student.