barking

Question
I have a 4 month old german shepherd, i take him to training classes but he barks at all the other dogs all the time except when he is working,he will meet dogs in the street go to them and smell then he starts barking.
He is fine with people,and dogs if they are not near him.
I hope you can give me some advice as i dont want it to turn to aggression.He is being neuted when he is 6 months old.Thank You.

Answer
Hold you hand in front of its face and say ''_______ enough'' while giving the leash a jerk.  If your instructor suggests something else, go along with it in class.  

The barking may not be aggression, just attracting attention to him self.  Good leadership and getting him neutered should head off aggression.