As with puppy schools, going to a good dog club is one of the BEST things that can happen to an adult dog. Before attending such a club the dog should, of course, a) be dog friendly with no aggression issues and b) ideally already know the basic behaviours in a non-distracting home environment.
The first dog clubs in Australia started in the early 1960s using correction based training methods. They were run by groups of enthusiastic volunteers and mainly geared, with great success for some of their members, to gain titles and trophies at obedience competitions.
Some inexperienced or sensitive dogs, whose first experience is in a large class at a conventional obedience club are so excited or stressed that no useful learning takes place. One or two bad experiences with an inexperienced instructor or another dog can easily teach a dog the wrong behaviour, cause mistrust, fear and aggression and take a long time to undo.
In recent years quite a few obedience clubs have gradually been able to change over to positive reinforcement training methods only. See the article by Dr Cyn D. Fisher, Professor of Management at Bond University and Chief Instructor (Obedience) at the Gold Coast Dog Club entitled 'Producing Change in Obedience Clubs', in the training articles section.
What exactly does 'positive reinforcement methods only' mean? In a nutshell it means that training is done without the use of any threats, intimidation or force. For a more detailed explanation see the articles in the 'Training Articles' section by Leandra Ford from Adelaide, "What is Positive Reinforcement Training?"