How to stop my dog from being aggressive?

Every time we go outside my dog barks at adults and kids.he doesn't like people getting close to him unless he knows you.Last week when we went to the vet my dog started barking at the people from the vet and when he was about to get his shots.I asked the vet if my dog could get training but they said "no" because he has to stop being aggressive.Should I get a second opinion by asking the dog trainers.My dog is only 5 months old.

I have the same problem with my dog, my vet never said anything about it. my dog is 4 which makes it harder to teach him because he's been doing the wrong thing for so long, 5 months old is nothing you'll be able to teach him faster. I wouldn't suggest going to a group class because the aggression will distract and bother other dogs/people, i'd hire a trainer to do private lessons with you at your house, one who brings their well trained dog which will help socialize him.

Do you know about 'Secrets to Dog Training' site?It has been online for 4 years. There is a lot of valuableinfo on how to train your dog and change its behavior.