There is a scene early on where a young boy cannot understand 5 X 5 in multiplication. He keeps getting it wrong. Is he being a smart apple, or did he really think he was right each time? He always had a smile when he answered.
Toto was trying to "cheat" the answer to him by pointing to the picture of the Christmas tree in his book. Christmas is the _25_th of December. Boccia didn't get it and said something even more stupid than previously, after which Toto looked frustrated and slapped his forehead.
Nope, there was no "smart apple" in his behaviour. The smart apple was of course the main character in his young age. The chalkboard kid simply had no idea, and the "Christmas" answer he gave, only amplified his stupidity. It was one of the few funny scenes in the movie. You clearly see that the boy struggles, you also see how he is in pain and shameful. He looks into the ground most of the time. He takes zero pleasure in getting smacked. I am surprised anyone could interpret the scene differently! I think the scene also had a meaning in underlining what kind of character the main person is/was - intelligent, liked mischief as a kid but still was kind at heart. (He did try to help the boy out!)