When students enroll in class they often say they are enrolling in a group class to socialize their puppy/dog.    On my Intake Form I ask a number of questions, many related to your dogs social history.  Recently I had someone contact me wanting to socialize her 18 month old dog who has been attacking other dogs on walks.  The dog recently escaped from their home and attacked a neighbors dog requiring Veterinary care.   The owner felt that bringing her dog to a class would help him learn to 'like' other dogs.   Another person emailed asking to enroll his 2 year old dog who 'needs to learn to calm down around other dogs'.  Apparently his dog comes unglued when they see another dog on walks.....barking....lunging....spinning in the air.   The owner said he felt being in a class would teach his dog to behave around other dogs and help socialize him. 

The common theme here is that most people do not understand what 'Socialization' is and that there is a specific time in a puppies life for optimal socialization.  From birth thru 16 weeks is when puppies are forming life long opinions of the world around them.  Everything they experience during this time is critical to their development.  The reason trainers strongly encourage ALL puppies attend a reward based class is to make the most of this critical developmental time in their life.  This is not to say that there is not some level of ongoing socialization thru out your dogs life, but true socialization happens during the first 16 weeks.   When puppies do not have proper socialization they are more at risk for problematic behaviors later in life. 

http://k9homeschooling.blogspot.com/2015/02/play-now-or-pay-later.html

By the time I meet an 18 month old dog who is reactive on leash...afraid of strangers and/or dogs....sound sensitive.......we are no longer talking about socialization we are talking about using behavior modification as a way to treat or manage  problem behaviors.   This can be a difficult conversation to have with clients as people don't always understand their dog is not suitable for a group class and needs a Behavior Consultation.    When I work with clients one-on-one we talk about the possibility of working towards a group class but we first have to lay a solid foundation for the handler and dog to prepare them to participate in a group class.  We also have to determine if the dog really wants to be in a group class, if their stress level is too high,  they are probably not benefiting from being in class and it may do more harm than good.  As an instructor I also have to take into account the other 5 people in class who may not appreciate having a dog bark the entire time, which is stressful for the other dogs and makes it hard for others to participate in class. 

A qualified Obedience Instructor will have a good vetting process for group classes so that owners can make the most of their training time and the best use of the money.  Not all Trainers have experience or credentials to handle behavior related problems so be sure to work with someone who has legitimate credentials. 

There are no short cuts or  fast tracking when raising and training dogs.  The time and training you put in during the early weeks will have life long benefits.  If your dog joins your family later in their life and already has established problems, don't loose heart, just understand that your training path will be different.