Waterproof Dog E-Collar Trainer with remote Rechargeable E-Collar for 2 Dogs

I have a very strong headed German Shepard puppy (about to be 1 year). I was at the end of my tolerance with him. I had even sent him to 7 weeks of training where they had him walking in public without a leash. But as soon as he got home, he remembered he was in charge here and back to not listening and doing what he wanted.