Is this a right sentence?

[tianhang]

My dear teachers, your help is needed here.
He is as good a student as his brother.
He is a student as good as his brother.
I know these two sentences are good English. But I am confused whether the following one is a right sentence.
He is such a good student as his brother.
I desperately need your help. Thanks!

 

[Raymott]

My dear teachers, your help is needed here.
He is as good a student as his brother.
He is a student as good as his brother. - This would be uncommon. I wouldn't use it.
I know these two sentences are good English. But I am confused whether the following one is a right sentence.
He is such a good student as his brother.No
I desperately need your help. Thanks!

He is such a good student, as is his brother. (This means they are both good students, but does not mean that he is as good as his brother).

 

[tianhang]

I know in your sentence as is used as a relative prounoun. So, you mean my sentence is not acceptable. Thanks. But different opinions are appreciated here. I once came across a sentence which goes He is not such a good driver as his wife. In negative form, we can use such...as..., why not in positive form? Thanks again.

 

[tianhang]

Hi, I am waiting for your help, dear teachers！

 

[Rover_KE]

Hi, I am waiting for your help, dear teachers！

Patience, tianhang. It's been the middle of the night over here.

But different opinions are appreciated here.

Have you considered that we may all have the same opinion as Raymott?

Rover

 

[tianhang]

I am sorry for pressing you, or rather annoying you. I am just eager to settle the problem.
Thank you! And now I can tell which is good English. But I am still confused how to explain the sentence-He is not such a good driver as his wife.

 

[Raymott]

I am sorry for pressing you, or rather annoying you. I am just eager to settle the problem.
Thank you! And now I can tell which is good English. But I am still confused how to explain the sentence-He is not such a good driver as his wife.

"Such" is such a difficult word word to explain properly.
But you cannot always take a negative sentence, remove the "not" and end up with a good positive sentence. This is especially so when set phrases such as "such a good" are involved. Other words, such as 'as', 'just', 'so' can cause difficulties like this.
It is difficult even for natives sometimes to explain why we say some things in various ways.

It's even quite possible that "He is not such a good driver as his wife." is actually not good grammatically. I would say, "He's not as good a driver as his wife."

 

[tianhang]

Thanks a lot! I really like your answer.