People are not purely products of their parents behavior. You have not only genetic variation, but a lifetime of all the incredible complexity of life experience that happens outside the house and with all other humans. I could imagine these factors moving each person backwards and forwards along any scale of “progress” we chose to measure people by, generation by generation, at times overwhelming the positive or negative influence of their parents.
This assumes that the kids themselves actually learn and grow at some point.
Some don't. It may be that the parents overcorrect and never teach their kids right/wrong, or it could just be the kid being a problem, or any number of other issues.