i took milu to sirius puppy school, and i like it.
Sirius Dog Training
i would say find out about the trainer. talk to the trainer to find out if you feel he/she is knowledgeable. at sirius puppy school, they have a bio page for all their trainers, so you can read about their experiences and trainings that they had.
also, make sure there aren't too many dogs in the same class, so you can get more attention from the instructor.
you can also look into puppy socials (check online to see if any is available in your area) it's helpful and fun way to socialize your puppy.