The Insurance Institute for Highway Safety released its second annual ratings of child car booster seats Tuesday, finding most models are not doing a good job of positioning seat belts to best protect children who use boosters.

Only nine of the 60 models examined were rated "Best Bets" for how they positioned children in lap and shoulder belts.

More states require boosters for children between ages 4 and 8, but there are no set standards for the seats.

Boosters are designed to elevate small children so that seat belts, designed for adults, fit them better and protect them better in case of a crash. A good booster routes the lap belt flat across a child’s upper thighs and positions the shoulder belt at mid-shoulder.

"What really matters is if the booster you’re considering correctly positions the safety belt on your 4- to 8-year-old in your vehicle. Our ratings make it easier to pick a safer booster for kids who have outgrown child restraints," said Anne McCartt, the institute's senior vice president for research.

The best-rated boosters are the Combi Dakota backless with clip, Recaro Young Sport highback (combination seat), Recaro Vivo highback, Maxi-Cosi Rodi XR dual-use highback, Evenflo Big Kid Amp backless with clip, Eddie Bauer Auto Booster dual-use highback, Cosco Juvenile Pronto dual-use highback, Britax Frontier highback (combination seat), and Clek Oobr dual-use highback.

Six boosters rated a "Good Bet." They are the Combi Kobuk dual-use backless with shoulder belt clip, Maxi-Cosi Rodi dual-use highback, Evenflo Symphony 65 3-in-1, Britax Parkway SG dual-use highback, Graco TurboBooster SafeSeat Wander dual-use highback and Graco TurboBooster SafeSeat Sachi dual-use highback.