甲级

Chinese ranking traditionally uses the Heavenly Stems (天干 tiāngān): 甲 (jiǎ) → 乙 (yǐ) → 丙 (bǐng) → 丁 (dīng), where 甲 is the top. So 甲级 = A-grade, 乙级 = B-grade, 丙级 = C-grade. Real estate, sports leagues, and professional certifications all use this system.

memory

甲 originally drew a seed husk cracking open — first growth, hence 'first / top'. Same character used for 'armor' and the first Heavenly Stem.