It’s one of those trained behaviors that’s SUPER simple to teach any dog, but really impresses your friends and family. But more importantly, it gives your dog a way to actually tell you he REALLY needs to go potty. This comes in VERY handy when you don’t happen to be in the same room with your dog when nature calls… but with the ringing of the bell, you can hear your dog asking to go outside from any room in your house!
Lindsay says of this study, "Schilder and Van der Borg (2004) have published a report of disturbing findings regarding the short-term and long- term effects of shock used in the context of working dogs that is destined to become a source of significant controversy ... The absence of reduced drive or behavioral suppression with respect to critical activities associated with shock (e.g., bite work) makes one skeptical about the lasting adverse effects the authors claim to document. Although they offer no substantive evidence of trauma or harm to dogs, they provide loads of speculation, anecdotes, insinuations of gender and educational inadequacies, and derogatory comments regarding the motivation and competence of IPO trainers in its place." 
Young puppies can’t hold their bowels & bladders for long. If you come home to find that they’ve had an accident in there it’s quite possible that they can’t hold it that long. Generally puppies can hold their bladder for about one hour per month of age. So your 3 month old pup can probably only hold their bladder for about 3 hours. If you’re going to be away at work for long periods of time see if you can get a neighbor, relative or dog sitter to come over to let your pup out during the day.
Before enrolling with a particular club contact them and ask if you can go to watch a class without your dog. This will help you decide if this is the right environment for you and your dog. Some clubs have waiting lists and you will need to book ahead, some accept people on a roll on roll off basis. Prices will vary from a joining fee and then weekly payments to a one off fee for a certain length of training.