Booster seat safety ratings released: Inside the report's results

(CBS News) The Insurance Institute for Highway Safety released a report Tuesday rating the safety of child booster seats, concluding that the more expensive models aren't always the safest.

It's all about how the seat belt lines up on your child, CBS News correspondent Jeff Pegues reported on "CBS This Morning." The lap belt should lie flat across a child's upper thighs, and the shoulder belt should sit snugly over the middle of the shoulder. According to the research, if children are in booster seats this way, it's the best way to keep them safe.

According to the Insurance Institute for Highway Safety, children in boosters are 45 percent less likely to sustain injuries in crashes than kids restrained by seat belts alone.

But some booster seats perform better than others. IIHS spokeswoman Jessica Jermakian said, "Research showed that boosters weren't doing a good job properly positioning belts on kids."

The IIHS began their tests five years ago and found that lap belts and shoulder straps on some booster seats did not properly fit children. But, this year, a record number of new models received the highest possible rating: 19 out of 31. Among them, the Evenflo Chase and the Graco Nautilus Elite.

Still, some new high-end models fell a little short. "One surprise was Britax," Jermakian said. "They changed some of their armrest designs on their boosters, and they missed the top rating for three of their new seats."

In a statement, the company says their products undergo "rigorous testing" and that they are working with "child safety advocates and vehicle manufacturers to ensure all Britax seats can be properly installed and used correctly each and every time."

Britax did receive the highest rating possible on some of their other models and says that it will make a slight change to these particular boosters so that seat belts fit better. Another surprising recommendation in the report: They say children should use a booster seat up to 12 years of age.

Watch Jeff Pegues' full report in the player above