For dogs suffering from serious behavior issues, such as leach reactivity or any type of aggression would not be suited in group classes environment. (peachtreedogtraining.com)
Please understand that for dogs who fit the following criteria would NOT do well in a group class environment (though we'd be happy to help set up a private training plan for you and your dog!) (thebarkboarding.com)
If your dog does not get along with other dogs and / or barks incessantly at the sight of other dogs, s / he may not do well in the group class environment. (eastbayspca.org)