My wife and I have two labs, brothers from the same litter, and seven months old. They have always played rough outside, tackling each other, wrestling, biting each other, etc. They don't growl when they play or bite hard enough to produce a yelp, and are fun to watch. They're like two bear cubs going at it. Yet lately, inside the house, they have begun to fight. My wife tells me that once a day she has to pull them apart because they just start fighting out of nowhere. We have an indoor pen so she puts the dog that she determines is the aggressor in the pen for 30 minutes or so. She says that 80% of the time the same dogs starts it and that it usually begins with the aggressive done eyeing the other. We talked to the breeder and she suggested this class which is $160 per dog and a seven week class. I don't mind paying the money but am hoping I don't have to. Any thoughts or suggestions would be appreciated. Thanks!!