poor student; underachiever
Refers to a student who performs poorly academically or is ranked low in a class. Often used in contrast with 優等生 (honor student). Can carry a slightly negative or self-deprecating tone.
He thinks of himself as a poor student.
He was an underachiever, but he worked hard and improved his grades.
優等生 is a top, exemplary student, while 劣等生 is a poor or struggling student.
Compound of 劣等 (inferior, low grade) and 生 (student). The exact historical derivation is uncertain, but the word follows a common pattern for describing types of students.