This is not “grade” in the same sense as “score” or “mark,” but the school year one is attending (ex: sixth grade).
학년←學年 (literally education year)
manuthchek / Maybe due to 1) Korean education system benchmarked a lot from the US 2) American English prevailing over the ones spoken in Britain and other Commonwealth countries in Korea
Well explained indeed! :D
“grade” in the same sense as “score” or “mark,” = 성적 = 성적표
GPA = 학점