
I would have a word with the trainers but if the others in the group are also puppies there may not be a problem as they be on a level playing field development wise.
You might find because he is without your collies he might even be overawed
At the club I go to we get lots of problem dogs of all ages that other clubs ban because they don't want to put in the extra work needed to help a dog with dog to dog problems
You can start by rewarding him if he ignores other dogs whilst you are out & you may even want to take him out on his own & do the about turn & walk away if another dog approaches & work on getting his concentraion & mind on you(difficult at such a young age but it can be done)& not on whats going on around him