The Border Jack is not a purebred dog. It is a cross between the Border Collie and the Jack Russell Terrier. The best way to determine the temperament of a mixed breed is to look up all breeds in the cross and know you can get any combination of any of the characteristics found in either breed. This hybrid is being purposely bred for the sport of agility and flyball. They tend to be very intense, busy dogs, that need a lot of activity. Not for novice pet owners, they need an activity and a lot of daily exercise. Not all of these designer hybrid dogs being bred are 50% purebred to 50% purebred. It is very common for breeders to breed multi-generation crosses.
"Frisbbe, the Border Jack (Border Collie/Jack Russell) at 6 months. He Hasn't grown much bigger since this picture. He's about 30 pounds. Very Smart like Border Collies and Jacks and very hyper as well."