Puppy socialization classes became a thing about 25-30 years ago. Before that, people took their dogs to obedience classes at 6 months or more and there was no "interacting" between the dogs. They were there to work with their handlers. Puppy classes nowadays happen when pups are between 8-18 weeks and they are a mixture of offleash play, techniques for dealing with puppy behaviors like chewing and biting, and some baby-level obedience like sit. Admittedly, puppy classes are adorable and people love the opportunity to show off their pups and they get the added bonus knowing that they are "doing the right thing." The problem is: What if its not? What if the puppy class you take your pup to is absolutely NOT the right thing -- either for that individual pup or for all of the pups?
Here is the deal: a poorly run puppy class can do more damage than no puppy class. All puppy classes are not created equal. You can have problems with the mix of pups and sadly, puppy classes are too often where the least qualified "trainers" are found. After all, what could be easier than watching a bunch of puppies play? But It should be the other way around. You need very experienced experts running puppy classes. Trainers with LOTS of knowledge about socialization, body language, fear periods and appropriate interactions. Ideally they also have a good understanding of breeds and breed types and how they differ in terms of play styles, rates of maturity, etc. Finally, they need to be able to see your pup as an individual and not just expect all pups of a certain breed to behave the same.
The problem is that the damage done by a poorly run puppy class often doesn't manifest itself right away but as your dog matures the problems arise and can be traced back to the formative experiences that dog had in puppy class. PLEASE, be sure to fully understand the credentials and training of anyone offering a puppy class. Loving puppies is simply not enough to qualify you! And if, at any time, your gut instinct in a puppy class tells you that something is not right or that its not a positive experience for your pup, then LEAVE. Right that moment. Don't worry about offending the instructor. You are your pup's advocate and you must always have your pup's short and long-term interest at heart.