I have a Nova Scotia Duck Tolling Retriver that goes everyday of the week to a dog-kindergarden. So the whole day stays with other dogs, plays, sleeps and whatever dogs do there. However, when we are walking on leash and he sees other dog he just pulls at max force thowards that other dog and becomes aggresive.
If he is out of the leash, then he starts to sniff the other dog and in 1-2 minutes he starts to ignore the other dog.
He may have also a leash problem, he likes to be always in front, but he also listens when I say to him on foot, then he stays closer. I plan to follow some instructions from here (Dog knows to stop on leash but still pulls) to improve this behavior.
PS: He has also a problem with skateboarders, I tried to make him confortable with a skateboard by riding one. At the beginning he barked at me, but then started to get used with it. When I went faster, he started to bark again, but I can say that even if now he doesn't have any problem with me riding a skateboard, it's when he sees other people riding that he gets aggresive.
Any advice how can I improve his behavior? Thanks!