sueobi kkeutnago naseo haksaengdeuri gyosireseo nawayo.

Because the sentence has two clauses, and each clause has its own subject.

• 수업이 끝나고 나서 = after the class ends
• 학생들이 교실에서 나와요 = the students come out of the classroom

So:

• 수업이 is the subject of 끝나다
• 학생들이 is the subject of 나오다

This is completely normal in Korean.

It means after ending or after it ends.

It comes from:

• 끝나다 = to end, to be over
• -고 나서 = after doing something

So 끝나고 나서 means after the class ends, and then...

The -고 나서 part emphasizes that the first action is completed before the second one happens.

It can feel a little repetitive to English speakers, but in Korean it is very natural.

• 끝나고 = ending, and then / after ending
• 끝나고 나서 = after it has ended

Both are possible, but -고 나서 makes the sequence clearer and a bit more explicit.

So:

• 수업이 끝나고 학생들이 나와요 = okay
• 수업이 끝나고 나서 학생들이 나와요 = also okay, with a stronger sense of after that is finished

Because 끝나다 and 끝내다 are different verbs.

• 끝나다 = to end, to be finished
  
  • intransitive
• 끝내다 = to finish something
  
  • transitive

In this sentence, the class itself is ending, so Korean uses 끝나다:

• 수업이 끝나다 = the class ends

If you said 수업을 끝내다, that would mean someone finishes the class, such as a teacher:

• 선생님이 수업을 끝내요 = the teacher ends the class

이/가 marks the subject, while 은/는 marks the topic.

Here, 학생들이 simply identifies the students as the ones doing the action.

• 학생들이 교실에서 나와요 = the students come out of the classroom

If you said 학생들은, it would sound more like:

• as for the students, they come out of the classroom
• or it could suggest contrast, like the students do this, but someone else does something different

So 학생들이 is the more neutral choice here.

들 is a plural marker. It makes it clear that we are talking about more than one student.

• 학생이 = student
• 학생들이 = students

But Korean often leaves plurals unmarked when the meaning is already clear from context. So 들 is helpful, but not always required.

에서 often marks the place where an action happens, but with verbs like 나오다, it can also mark the place something comes out from.

So 교실에서 나와요 means:

• come out of the classroom
• literally, come out from the classroom

English uses from or out of, but Korean naturally uses 에서 here.

Both can involve leaving a place, but the viewpoint is different.

• 나오다 = to come out
• 나가다 = to go out

A simple way to think about it:

• 나오다 focuses on movement toward the speaker or toward an outside viewpoint
• 나가다 focuses on movement away from the current place

In English, both may sometimes translate as leave or go out, but Korean keeps this viewpoint distinction more clearly.

It is a contraction.

• dictionary form: 나오다
• stem: 나오-
• polite ending: -아요

So:

• 나오아요 becomes 나와요

This kind of contraction is very common in Korean.

Another similar example:

• 보다 → 봐요

나와요 is in the polite -아요/어요 style.

It is also non-past, which means it can express:

• present
• habitual action
• near future, depending on context

So this sentence could mean something like:

• students come out of the classroom after class ends
• the students are coming out of the classroom after class ends

The exact time sense depends on the situation.

Some parts can move, but Korean usually puts background information first and the main verb at the end.

That is why this order is very natural:

• 수업이 끝나고 나서 학생들이 교실에서 나와요

It starts with the time/background part:

• after class ends

Then it gives the main action:

• the students come out of the classroom

You could move some elements for emphasis, but the verb of each clause usually stays near the end of its clause.

Yes, that can also be said.

Korean sometimes uses 을/를 with places that someone leaves or passes through. So 교실을 나와요 can mean leave the classroom or come out of the classroom.

Still, 교실에서 나와요 is very natural and very clear for learners, since it straightforwardly shows the starting location.

So both can be possible, but 교실에서 나와요 is an excellent standard pattern to know.