This is another show that's good, but definitely not for children. Jo Frost knows her stuff, and it shows. The show's most positive point is that families truly come out appreciating each other more and behaving better toward each other after using her techniques. And Jo will pull no punches if a parent is lazy, a pushover, or abusive.
The danger to kids is that they will either think the behavior is funny and/or imitable (backtalking teenagers, aggressive, foul-mouthed children), or that they will absorb negative messages about their own parents. For example, one thing I don't agree with in this show is, the father is rarely if ever a positive leader in his home. He is either a pushover, a whiny extra child, or a blowhard who smacks his kids around and acts like his wife should stay in the kitchen. Meanwhile, the wives can be pretty whiny, aggressive, or doormat-ish themselves. These are not families, at least in the beginning stage, that discerning parents, especially those of the Judeo-Christian persuasion, should ever emulate. On another note, on the two occasions Christianity plays a role, it's negative (one mon says "I forgive you" while spanking her daughter; the other Christian parent is a preacher who doesn't step up to the plate at home). Heavy language is bleeped, but there are instances of milder profanities and negative words, even down to a three-year-old threatening his mom. Kids kick, hit, bite, and in general beat each other up, and yes, I do consider spanking negative. (One father repeatedly smacks children with his belt on camera).
In short: parents and mature teens can watch, and as noted, they can learn valuable techniques from Jo. But kids, you're not yet ready for this nanny.