All dogs need to be exercised everyday in some form or fashion. The most common method is through the walk around the neighborhood, but is a short walk around the block enough exercise for your particular dog?
Half the battle of dog training is finding the right training class and the right trainer to assist you along the way. Not all dog trainers or classes are created equal! There are a lot of differences among trainers, and you need to be prepared to find the best one for you and your dog.
For the health and wellbeing of your dog, training should really not ever be considered an option when owning a dog. Well trained dogs are more likely to be behaved and listen, be void of behavioral issues, be good in public, and are less likely to bite. Owners also have a much closer connection with the dog when the time is taken to form a relationship through training.