Why does your 5 year old son start writing with his left hand and finishes with his right hand?

it is probably easier for him i used to be like that but i settled into being left handed The boy has not yet " decided " which hand he will use to write with. At a certain point, his brain will decide on left or right "handedness " Don't push him to use one hand, over the other, let him find out for himself. Do encourage him to "keep on writing " with either hand.