Puppy Stresses around other dogs

Hello!

Took my 6 month golden to their first puppy foundation class. We practice a lot of the basics at home so we were fairly confident in the sit/down/stay etc. however we wanted the pup to do this amongst other dogs.

When we were sitting in a large hall with about 9 other dogs, our dog just wanted to meet all of the pups. He wasn't allowed to so he began to bark (other dogs were also barking).

This made him quite stressed to the point he was heaving. When the obedience exercises began he was fairly good and not focused on meeting other dogs. The issue was in between exercises where they were all told to lay on the mats.

I want to try to eliminate this stress for the next few times, or work towards it. Any suggestions that could helpy dog would be much appreciated.

Ps. The trainer suggested we get him to focus on us when he barks. And suggested the relaxation protocol out on the park.

Cheers!