The drive and will to please of a chessie is second to none. They are hard headed and tricky to train. You have to have patients and brains. You have to sometimes make him think it was his idea. As for aggressive that is all on the owner. From the day I got my pup I would take him every place I could. Stores, banks, parks, you name it I got him around as many types of dogs i could of all sizes and temperments, as well as every little kid I could. He' s now a year old and not agressive to kids or dogs (unless alone in the car or the house). They are very protective. He' s a big goof. If you want to know more e-mail me, I also know where you can get one around X-mas time from a great breeder for a VERY good price!!!!! If you go chessie you won' t regret it.