...two blackened eyes - almost swollen shut,"

Pain.  My student was in pain.  How could I expect him to learn when he was in such pain?  The truth of the matter was this.  I didn't.  I knew the score.  Sometimes people took a beating for no other reason than they were in the wrong place at the wrong time and someone was having a bad day.  In this case, my student was getting ready to go home.  Home to family and friends and a life outside of the prison.  Some offenders didn't like it when others got to leave.  They resented the fact that they would remain inside while others would enjoy there fruits of their freedom, so they would sometimes beat their soon-to-be-free comrades.  It didn't happen all of the time, but it happened often enough.  And sometimes the beating was pretty bad.  Like in this case.

So when I saw him come into my classroom, I pushed aside any thoughts I had about teaching him.  Teaching was not what was important at that moment.  Recognizing his pain was.  It was a touch of humanity, and it is this touch of humanity that moves readers.

It is worth noting that I did not sit down and write this passage with the intent of provoking an emotional reaction in the reader.  I simply wrote...knowing that it moved me.  And still does.  Your writing must move your readers.