Formal students had very good performance in their academic grades, but the informal students didn't, and really sucketheir performance was quite bad.

I was a bit surprised to see you use the word "sucked" because your writing felt quite polite and formal, and sucked is somewhat rude. It's not very rude, but I just don't think it fits the tone of what you're writing.

One year, my school recruited a class of formal secondary specialized secondary students, and there were five female students in the class.

Formal students hadgave very good academic performance in their academics by getting good grades, but the informal students didn't, and really sucked.

OneA year later, in a casual conversation with the head teacher of the class, I learned that a few of the female students were dating some informal students.

I asked the teacher if the female students had ever dated those formal students, and he said, no.

I got confused because I would've guessed that the formal female students shwould've dated the formal students instead of the informal students, but the facit was totally oppositthe reverse.

When we guess or assume something, we use the subjunctive case. This is tricky and worth looking up.

We often see from TV shows that a few very goohen we watch TV shows, we often see well-mannered ladies fighting fover a jerk who is not handsome, has no money, no status, no good manners, butwhile the only thing he is very good at is to cheating on women, to win the favor of women.

We're not all like this!

I know what you mean but I had trouble thinking of substitutes for "a few very good ladies."

Here are my attempts:
well-bred
pretty
beautiful
educated