我哥哥是中学生。

Wǒ gēge shì zhōngxuéshēng.

My older brother is a middle school student.

我以前是中学生，现在是大学生。

Wǒ yǐqián shì zhōngxuéshēng, xiànzài shì dàxuéshēng.

I used to be a middle school student, now I’m a university student.

很多中学生喜欢打篮球。

Hěn duō zhōngxuéshēng xǐhuān dǎ lánqiú.

Many middle school students like to play basketball.