The U.S. government is announcing new safety measures for school buses.

All buses will need to have higher seatbacks, four inches higher than today's standard.

Smaller school buses carrying less than 15 passengers must have lap and shoulder seat belts.

Seat belts in larger buses are still not required. That's because the government says the rule could force schools to transport fewer kids.

Officials insist that higher seats are even more important than seat belts.

"We believe the high-backed seats offer added protection," said John Matthews, transportation director of Montgomery County Schools. "Going from 20 - 24 inches just increases the size of that egg carton around the student or the compartment that keeps them protected."

The new safety requirements go into effect in 2011.