Keep all the grades of the students who passed the test as is, and
convert the grades of all the students who failed to 54.
Related:
The following appeared in the editorial section of an educational publication.
"One study at Lee University found that first-semester grades of teenage students who had always attended public, tax-supported schools were slightly lower than the grades of students who had received some home schooling instruction by parents at home, although the grade differences disappeared in the second semester....