Small practice

The exam was coming to the end.

The professor had written something in the student's record book and closed it. shut it down.

The student took it and gave a look inside.

better:

The student took it and looked inside.

Oh my God! You put gave me E!

It is unfair, you are preconceived! I heard the rumors about your persnickety, but hope it all was a lie!

You can say somebody has preconceived ideas, but it is rare to call somebody, "you're preconceived."  Also, no normal English speaker would use the word persnickety like this in every day language.

You are a sassy/impudent young man! Do not blame me on for your bad marks!, Blame your sluggishness in study!

The  teacher throttled?? his papers angrily. He acknowledged well all the tweaks made by his students.
Your sass is unparalleled! My estimation of you knowledge is ultimate!
The student shut his book and quickly ran away from the class.

The English sentences are fairly well written but your choise of vocabulary is not correct at times.

You not only have to know the word, but you have to know it's connotation, dennotation and how to use a word.

Take the word childish, for example.

The dennotation or dictinoary meaning, is: of, like, or appropriate to a child.

Imagine a teacher is playing with her students and she's happy, enthusiastic, and behaving like a child.

You could write,  The teacher played with the students with a childish enthusiasm.

However, the word childish has a negative connotation.

Usually it is used to describe something silly an immature.

So to an English speaker now the sentences reads as,

The teacher played with with the students with an immature/silly enthusiasm.

And that is not the idea that wants to be conveyed, so maybe it is best to write:

The teacher played with a childlike enthusiasm.

Although childish and childlike have a very similar dennotation, the connotation of both words are very different. One is positive, the other is negative. Therefore when you write, you need to know how the words are used, otherwise, your readers might be confused.