Follow directions please!!!!!!!!!!!!

I don't know if anyone else is having this problem my 4 yr old db is driving me crazy, literally. I tell him to do something and it's like a party to him. He has every intention on doing it but he gets distracted by the littlest things, like if he walks past my dd who can playing by herself, he'll stop and play with her. I have no idea what to do. I think to myself, what is wrong with this boy. Here is the kicker though, he gets smiley faces at school all week, but when he gets home he's like a different kid. He's hypered and hard headed. Any tips on what to do? I am confused and I have a headache dealing with day in and day out.