Kenny is the middle child of the Watson family and as a result feels left out because all the attention is received either by his older brother, Bryon, who is a rebel and constantly getting into problems at school, or by his younger sister, Joetta. It is clear that he has few friends at school. The only friend he did have only used to play with him because he could steal dinosaurs, which Kenny considers to be a "fair trade." Kenny has two problems at school that unfortunately mark him out as a target to be bullied and shunned.
Firstly, Kenny is very good at reading and enjoys it a lot:
Teachers started treating me different than other kids when I was in the first grade. At first I thought it was cool for them to think I was smart but then I found out it made me enemies with some of the other kids.
The most humiliating moment for Kenny comes when he is forced by a teacher to read in front of Byron's grade to set them a good example of what they could achieve. This intelligence makes Kenny get bullied a lot, and the other kids of the school call him Pointdexter.
Secondly, Kenny has a "lazy eye," which, in spite of many efforts to correct it, still remains looking in a different direction from Kenny's good eye. The result of this, in addition to his intelligence, means that Kenny is a natural target for being bullied, in spite of having the protection of Byron:
I still had to fight a lot and still got called Cockeye Kenny and I still had people stare at my eye and I still had to watch when they made their eyes go crossed when they were teasing me.
Thus we can infer that Kenny is a sensitive boy who is ostracised socially at school because of his intelligence and his eye. As such he is lonely and spends lots of time by himself.