If you want to prevent accidents before they happen you’re going to need to watch your pup at all times, including every time they wander off. It only takes one accident to set your training back. Now I know that watching your puppy non-stop isn’t exactly fun & exciting, but being able to catch them before they have an accident is why this method works so well.
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.