More aboutcomputer fans turn clockwise anticlockwise
No, not all fans turn the same direction. Some fans pull air into the case and some push air out of the case. Why are you asking this question?
my son has taken the fans and apart and is not quite sure how they go back in
You'll have to feel to see what direction the air is blowing out of them. Fans on the front of a case are usually intake fans that suck air into the case. Fans on the back are usually exhaust blowing the hot air out of the case.