I had a puppy like this in one of my classes once. He was a small puppy, and he bit hard. It did look like play, but it was so much more intense than you usually see in pupppies (and yes, by that time I'd had hundreds of puppies), and I really did feel that as an adult, he'd probably bite some person at some point. In addition, of course, he had owners who weren't really committed to having a dog at all, and really didn't want to do any training with him. They ended up dropping the class, and I believe they rehomed the dog (it's possible, though I honestly don't remember specifically, that I suggested rehoming).
All that said, I like adojrts' advice. Unfortunately I didn't know that game when I had this puppy in my class, but I really think he'd benefit from it (although honestly, his family would probably never practice it, or if they did they'd do it wrong).