noun
same school year; same grade
Refers to being in the same year/grade at school. Often used in contexts like 同学年の友達 (friend in the same grade) or 同学年で一番 (best in the grade).
彼とは同学年で、よく一緒に勉強した。
He and I were in the same school year, and we often studied together.
同学年の生徒の中で、彼女が一番背が高い。
Among the students in the same grade, she is the tallest.
同年 means 'same year' in a general sense (e.g., same calendar year, same year of birth), whereas 同学年 specifically means the same year in an educational context.
Compound of 同 (same) + 学年 (school year/grade).