Paddy Clarke Ha Ha Ha- Post 3

In the passage where Patrick's teacher demands he shows his mother Sinbad's ruined worksheet, I found it interesting when he decides to go against his orders. Before this point in the story, Patrick has always been a horrible older brother. He would insult Sinbad, cause him physical harm, make him cry, and needlessly ridicule him in the presense of friends, but only now does he do something good for him of his own accord. Does this passage suggest that there could be a loving brother somewhere within Patrick's otherwise mischievious soul? Or did he just wish to spite his teacher by disobeying his order?