There are some scholars who believe that this quote from Confucius is about taxes. They believe this because taxes were paid in grain which was grown on square plots made up of nine sections. Eight families would work together on all nine sections and the center section would be collected by the government.
Ahhh taxes, well at least we don't have to pay them in grain anymore...
Anyway... I don't think Confucius was talking about taxes.
What I love about this quote is it really shows the reciprocity that is key to understanding Confucius. It even implies cosmology--a cosmology where everything is mutually self-re-creating.
If I show the student one corner of the square, it is the student's job to show me the other three. That is not my job. It is the student's job to bring significant energy and commitment to the lesson.
One the other hand, if the student doesn't respond to my lesson I don't look to criticise the student. I first reflect and then acknowledge that I'm not offering a teaching which meets the student where they are, at their learning level or interest. A good teacher will move on to a new subject or try a new approach.