This is the 661st most frequent Japanese word.
高校生
High school student.
In this sentence, '高校生' is used as a noun to describe the identity or role of the subject, which is 'a high school student'.
私は高校生です。
I am a high school student.
Here, '高校生' is used to represent a general group of people, specifically all individuals who are high school students.
高校生はよく数学を勉強します。
High school students often study mathematics.
In this case, '高校生' indicates a state or stage that someone transitions into, showing a change in educational status.