Ha, my less than 12 year sons were taller than their mother, this is from the NHTSA website.
"Please keep in mind that placing a child in the front seat, no matter what the circumstances, comes with increased risk. Frontal impact crashes represent 59 percent of passenger vehicle "tow-away" crashes and result in 38 percent of passenger-vehicle occupant fatalities (2002-2006 National Automotive Sampling System - Crashworthiness Data System, 2006 Fatality Analysis Reporting System). NHTSA recommends that children 12 and younger ride in the rear seat in the appropriate child restraint system: an infant in a rear-facing infant seat, a child in a forward-facing child restraint, an older child in a booster seat, and a child who is large enough in an adult seat belt. (For additional information on appropriate child safety restraint systems, see NHTSA's."
Generally for unbelted occupants, airbags are only good for speeds under 25 mph. Another major problem with these things, one size does not fit all, wife is only 5'2" tall, her head is very close to that bag. A short friend, male, got his neck broken in a minor fender bender accident, not to mention people, even mechanics, getting injured by these things when having to remove them for other service.
More children were killed by these things than adults saved that refused to wear their safety belts, law say to put your kids in the back seat, what back seat? Babies under a year old are required to have rear facing seats, most driver's can avoid a head on collision, but are completely helpless when being rear ended.
So much for the law, but is the law and must be obeyed, or will cost you a fortune in fines.