The school is well-known for its midnight-oil homework.

[Silverobama]

My city is still developing very fast. Primary school students are very busy as far as I know. One school in my city is very famous not for its education level but for its homework which are assigned to the students. One of my students studies there and almost every day she needs to do her homework till the midnight.

I wrote "The school is well-known for its midnight-oil homework” to express this idea.

Is it italic sentence natural? The tone of saying it will be sarcastic.

 

[tedmc]

I have heard of "burn midnight oil" which means to stay up late to do work/homework, but not "midnight-oil homework". Idioms are set phrases which would not sound natural if they are modified like you have done.

 

[teechar]

My city is still developing very fast.

That sentence is irrelevant to the rest of the post.

Primary school students are very busy as far as I know.

That's not how "as far as I know" is used. "As far as I know" means "to the best of my knowledge".

One school in my city is very famous not for its standard of education level but for its the excessive homework which its students are assigned. to the students. One of my students studies there attends that school, and almost every day, she needs to do her homework stays up till the [ no "the"] midnight doing her homework.

I wrote "The school is well-known for its midnight-oil homework” to express this idea.

Is it italic sentence natural? The tone of saying it will is supposed to be sarcastic.

No. That sentence is no good.

 

[BkeKay]

The use of italics in your sentence can definitely convey a sense of sarcasm, emphasizing the ironic nature of the school's reputation for late-night homework. It adds a bit of emphasis to the idea that the homework load is excessive.