Why Don't School Buses Have Seat Belts?

I subscribe to this spam mail service called Ask Yahoo! which answers a question from readers everyday. I've often asked myself the same question about seat belts.

The National Highway Traffic Safety Administration argues that seat belts aren't the most effective way to protect passengers on school buses. Instead the big yellow beasts employ something called "compartmentalization." Think back to your days on the good ol' school bus. Remember how those rigid green seats were wedged closer together than on even the cheapest no-frills airline? That's compartmentalization in action. Sitting in "strong, closely-spaced seats that have energy-absorbing high seat backs," passengers are effectively protected from crashes...

If you need answers to something and are willing to pay, visit Google Answers. They are a great bunch of researchers. You may wish to pay me to answer questions, but only if there're simple enough haha...