Did... did he just draw something with no hidden message in it?
Seems like it, until further notice- this kid deeply loves his dog, all he does draw pictures about his dog... and his grades are suffering from it (see in the garbage can). Two backpacks, homework that seems to be undone, and more drawings of his dog- I think this kid and his dog are afraid of the thunder because it sounds like his parent(s) shouting. A guess, but still.