It shouldn't be that hard. Then again, his grades are bad, so perhaps it's understandable; he's not the strongest staphylococcus colony on the petri dish.
Yeah, I've gotta agree with Kaarme. The extreme lack of depth perception is a bit of a stretch.
How old is his sister supposed to be? 12, 13? I think they said middle-school at some point. I guess at that age it's not too weird, especially considering that dad doesn't seem to be around much, but I hope she grows out of that brother-complex before too long