What's Wrong With Kotoro

Kotoro is an eight year old chap built like a sumo wrestler. I teach him once a week and I am always fearful that he could cripple me if I raise my voice in reproach towards him. I wouldn't be so worried if he was a sweet kid, but he is violent, loud, and unstable. In fact, he is pure evil. He always enters the classroom hollering with sweat dripping off his chubby face and chocolate smeared across his mouth whilst he clatters into the walls. Initially, I believed he was shouting in Japanese, but on closer inspection it's nothing more than gibberish.
"Wa wa ba ba!" is his favoured tune.
I tell him to shut his goddamn mouth in the most polite way, and he will immediately come marching towards me in a fit of anger, stand in front of me and gnash his teeth like a pit-bull.
I have to treat Kotoro carefully because anything can set him off. This is the reason why I never place any teaching objects on the table because he will only vandalise them. For instance, I will put a pack of alphabet cards on the table - he'll fling them like boomerangs; I will put colouring pencils on the table - he'll snap them in half and stick them up his ass; I will put a dice on the table for a board game - and he'll eat it. It's a no win situation.
There are about 10 other kids in the class, but my main focus is keeping Kotoro happy and studious.
I have toyed with the idea of allowing him to devour a KFC king sized bucket whilst I teach, but realized he would never pay attention to me.
It has been a long nine months teaching this kid. The low-points have included him marching around the classroom with his dick hanging out whilst singing the Japanese national anthem. On another occasion he squatted over a bin and did a shit in it before sitting on the faces of other students.
Quite unexpectedly, though, I found his Achilles heal.
I had given the kids a jigsaw puzzle to do. I was amazed to observe that Kotoro was quiet and polite to the other kids as he carefully tried to complete the puzzle. When the kids finished the puzzle, he alone packed away the pieces delicately as if this act was the most important thing he had ever done in his life. The kids were getting restless because I was staring dumbfoundedly at Kotoro for five minutes as he packed away the puzzle.
When he handed me the puzzle box with a bow, I thanked him with a stunned gasp, thinking that I must bring more puzzles to the lessons so I can restrict his fondness for causing carnage.
When he delivered a final bow he ran over to the boy next to him and sat on his face.