Is not as good as would be expected of an undergraduate

Is not as good as would be expected of an undergraduate
 

What are the other ways of saying a person's Japanese is not up to scratch? Are my sentences natural English?:

-He does not even know undergraduate/junior secondary Japanese.
-His Japanese does not reach undergraduate/junior secondary standard/s?

His Japanese doesn't not exceed undergraduate levels or the undergraduate level.

His Japanese is very elementary.

Thank you, Poli, but were my sentences natural English?