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There's an English speech contest at Lisa's school this Friday. Lisa's teacher asked Lisa to enter the contest because her English is good, and she works hard.

Since Lisa is a student, why not use studies hard?
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You could say that if you wanted.
Comments  
Teachers: We supply a list of EFL job vacancies
The words "works" and "studies" are almost interchageable if you are using them in certain context.

Like here:

What is your job?

I am a student.

* The word job is synonymous with the word task.

That's my one cent.

My Q.

Can I say, " I am student." here?
No.