I am not arguing with unknown facts. But, simply check the grades he was in, and corresponding years.
1955- 5th year(grade 5)
56- 6
57- 7
58-8
59-9
60-10
61- 11th year (O/L exams)
62-12
63-13
64- 14th year (A/L exams)
Only a student who failed the exams and had to repeat the same grade twice will be eligible to attend the 14th year at school.