and just as a further comment on how I train
Generally, at around 8 months old pups will start exerting independence. Your choices are to win your dog over to seeing your view and want
to work with you or to start correction to make
your dog work with you.
I start at a young age teaching them interactive games which helps to lessen the effect of training time versus play time. I give my dogs plenty of dog time where they can sniff and dig and roll and generally get to know their environment (this is important throughout their life). When in new environments throughout their lives, they are allowed to explore but this is especially important between 8 months and 2 years.
So, when the 8 month 'I dont wanna' phase hits, I actually pull them from classes if they cannot focus and work on basics in slowly increasingly distracted environments. I give them the games and foundation I will need as they mature. Such as touches, spinning, jumping on me, tugging etc in ever increasing distraction. If my dog can choose me over his environment AND take treats, toys, play rough & tumble games etc in a variety of environments I will then restart classes. If they cannot handle that level of distraction, I work away from the group on simple focus games until they are ready ( distance, distraction, duration) to perform simple tasks and take treats & toys. Sometimes they simply sit on my lap and observe (I need to train to a mat but somehow I never seem to get around to it LOL) If your dog will take treats & toys at home but not in a class environment you need to make a choice -- choose distance / distraction parameters or use correction -- or work in quieter environments -- the refusal to take treats is especially indicative of high stress levels.
I am a cross-over trainer and can state that correction versus non-correction methods of training both have their strong (and weak) points. They take about equal amounts of time to train. I started training way back in the 80s so I do know both sides of the equation.
So in summary, your puppy is progressing in a perfectly normal way --- he has to get to know & feel safe in his environment. He needs to choose you over his environment but this is a learned skill. He needs the tools to let you know he is ready to engage (or a solid 'READY' command).