shàngkè de shíhou bié dàizhe ěrjī tīng yīnyuè.

It means during class or when class is going on.

• 上课 = to be in class / to have class / to attend class
• 的时候 = when, at the time of, or during

So 上课的时候 is a time expression meaning when class is in session.

In this pattern, 的 links a verb phrase to 时候.

Structure:

• [verb phrase] + 的 + 时候

So:

• 上课的时候 = the time when class is happening

This is a very common pattern in Chinese:

• 吃饭的时候 = when eating
• 下雨的时候 = when it rains
• 小时候 is a fixed word, but in general 的时候 often works this way

In casual speech, native speakers sometimes shorten it and drop 的 in some expressions, but 上课的时候 is completely standard.

别 means don’t in commands or prohibitions.

So:

• 别戴着耳机听音乐 = Don’t wear earphones/headphones to listen to music

别 is very common in spoken Chinese when telling someone not to do something.

Compare:

• 别说话 = Don’t talk
• 别走 = Don’t go

A longer version is 不要, which also means don’t:

• 上课的时候不要戴着耳机听音乐

That version is also correct, but 别 is shorter and very natural.

着 shows a continuing state.

• 戴 = to put on / to wear
• 戴着 = to be wearing, to have on

In this sentence, 戴着耳机听音乐 describes listening to music while wearing earphones/headphones.

So 着 helps show the state accompanying the action:

• 戴着耳机 = with earphones on

It sounds natural because the sentence is talking about an ongoing situation during class, not just the moment of putting them on.

This is a common Chinese pattern where one action or state happens together with another action.

Here:

• 戴着耳机 = wearing earphones
• 听音乐 = listening to music

Together:

• 戴着耳机听音乐 = listen to music while wearing earphones

You can think of 戴着耳机 as describing the manner or accompanying state of 听音乐.

Similar examples:

• 站着说话 = speak while standing
• 躺着看书 = read while lying down
• 拿着手机聊天 = chat while holding a phone

Chinese often puts the main action after the time phrase and after any accompanying state or manner.

Structure here:

• 上课的时候 = time
• 别 = negative command
• 戴着耳机 = accompanying state
• 听音乐 = main action

So the sentence moves in a natural order: During class, don’t, while wearing earphones, listen to music.

In smoother English: Don’t listen to music with earphones on during class.

耳机 can mean either earphones or headphones in everyday Chinese.

The exact type is usually understood from context. If someone wants to be more specific, they might say:

• 耳塞式耳机 = earbuds / in-ear earphones
• 头戴式耳机 = over-ear headphones

But in normal speech, 耳机 is often enough.

In Chinese, the subject is often omitted when it is obvious.

This sentence is a command or rule, so the understood subject is usually you:

• (你)上课的时候别戴着耳机听音乐。

Leaving out 你 sounds natural and normal. Chinese often avoids repeating subjects when the context is clear.

The sentence specifically includes 听音乐, so the full idea is:

Don’t wear earphones/headphones to listen to music during class.

Because 听音乐 is stated explicitly, the focus is not just the earphones themselves, but the behavior of listening to music in class.

If you wanted to say only Don’t wear earphones in class, you could say:

• 上课的时候别戴耳机。

Yes. 上课时 is a shorter version and means the same thing: during class.

Compare:

• 上课的时候别戴着耳机听音乐。
• 上课时别戴着耳机听音乐。

Both are correct.

Difference:

• 上课的时候 sounds a bit more conversational and slightly fuller
• 上课时 sounds a bit more concise and sometimes a little more formal or written

Chinese often puts time expressions near the beginning of the sentence.

That helps set the scene first:

• When? During class.
• What should not happen? Wearing earphones and listening to music.

This is very natural Chinese word order.

You could think of the structure as:

• Time + command

Examples:

• 晚上别喝咖啡。 = Don’t drink coffee at night.
• 考试的时候别说话。 = Don’t talk during the exam.

Here it basically means when class is in progress.

上课 can have slightly different English translations depending on context:

• a teacher: to teach a class
• a student: to attend class
• more generally: class is going on

In 上课的时候, the important idea is simply during class time.

Yes, 在上课的时候 is grammatically possible, but it is usually less natural here than simply 上课的时候.

Chinese often does not need 在 before this kind of time expression.

So:

• 上课的时候别戴着耳机听音乐。 = more natural
• 在上课的时候别戴着耳机听音乐。 = understandable, but a bit heavier

It sounds like a rule, instruction, or warning.

Because it uses 别, it is a direct negative command:

• Don’t do this

Depending on context, it could be said by:

• a teacher
• a parent
• a school sign or rule
• a class monitor

It is not extremely rude, but it is clearly telling someone not to do something.