hijacking wireless information

Ok, I want to see if its possible for me to hijack my sons information while he is on his laptop and I am on mine. I don't want to have to install anything on his laptop. I have a feeling he is up to something and I've asked him but something tells me he is lying to me. I just don't want him to feel like he can't talk to me. I know this isn't the best way, but this is the path I've chosen. Is there a way to do this?