High School Student
High Schooler
noun
You know 高校 means "high school." So, a "life" that does high school is a high school student. This is like how 中学生 are middle school students and 小学生 are elementary school students!
こうこうせい
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. Use the reading of 高校 from before to learn the reading of this word as well, if it helps.
今日は、高校生たちが、このパン工場の見学に来ます。
Today, high school students are coming to this bread factory on a field trip.
わたしは高校生の時、毎日のように海に行っては魚をとって食べていました。
When I was a high school student, I would go to the sea every day to catch fish and eat them.
あいつはただの高校生デビューだよ。
He's just trying to look cool because he’s in high school now.