중학생 (chunghakssaeng) means “middle school student”

More examples

중학생 때는 공부 외에도 다양한 활동을 해 보세요.chung hak ssaeng ttae neun kong bu oe e do ta yang han hwal dong eul hae po se yo

In middle school, try various activities in addition to studying.

A learner in the school stage between elementary school and high school.

학생hakssaeng: A person who attends school as a learner.
초등학생chodeunghakssaeng: A student attending elementary school.
고등학생kodeunghakssaeng: A student enrolled in high school.

중학교 학년에 속한 학생을 가리키는 말chung hak kkyo hang nyeo ne so kan hak ssaeng eul ka ri ki neun mal

중학생 (junghakssaeng, "middle school student") is formed from 중학 (junghak, "middle school") and 생 (ssaeng, "student suffix"), which marks a student.

English speakers may associate middle school with a fixed age, but school stages differ across countries, so this label is best understood by school stage rather than age.