class vs grade level in Korean
수업vs학년

수업class
수업 means a class, lesson, or study period, usually at school. You use it when talking about having class, starting class, or what kind of class you take. It is a very common word in everyday school life.
When to use class
학년grade level
학년 means a student's grade level or school year. You use it to say what year someone is in at school, such as first grade or third grade. It is common in everyday talk about school, children, and classmates.
When to use grade levelHow they differ
학년 means your school year, like first grade or second year of middle school. 수업 means the actual class or lesson you attend.