In the pantheon of child development, many parents consider the act of turning the car seat from rear-facing to forward-facing right up there with the first step. Traditionally, they’ve happened around the same time — Baby’s first birthday — but on Monday, the American Academy of Pediatrics (AAP) officially revised its recommendations regarding buckling up babies.

Babies should remain rear-facing until age 2, and their older siblings should use a booster seat until they’re at least 8.

The AAP policy, published in the journal Pediatrics, was last updated in 2002, when it advised that babies should be at least 12 months old and 20 lbs. before riding forward-facing. But research has shown it’s best to keep babies rear-facing as long as possible — certainly until they reach the maximum height and weight for their seat. A 2007 study in the journal Injury Prevention that found that children under age 2 are 75% less likely to die or be severely injured in a crash when in a rear-facing car seat. (More on Time.com: Babies Who Start Solids Too Early More Likely To Be Obese)

In terms of anatomy and physiology, children are not just small adults. Their heads are large in relation to the rest of their body. “That’s what makes them cute, but their heads are relatively heavy and their necks are constructed differently,” says Dennis Durbin, lead author of the policy statement and a professor of pediatrics at the University of Pennsylvania. “When a child rides rear-facing, their head and neck are better supported in the event of most crashes.”

Still, most parents could barely wait for Baby to blow out the candles on the first-birthday cake before excitedly turning the car seat around. Riding forward-facing seems so much more interesting.

Yet in the nine years since the policy was last updated, Durbin says, there has been an “explosion of scientific evidence.”

As a result, most car-seat manufacturers have reconfigured their child restraints, deepening the seats so that nearly all can accommodate children up to 35 lbs., a weight most children don’t reach until after age 2.

All states have laws requiring car seats for children up to age 4. Most also have laws mandating boosters for older children, but the parameters vary widely in terms of age limits. Durbin hopes the new recommendations will spur states with younger age limits — some as young as 5 — to increase them to age 8. (More on Time.com: American Academy of Pediatrics: Make the Flu Shot Mandatory)

But age isn’t even the best way to gauge how long your child should keep using a child restraint. The recommendations use age because it’s easier for parents to remember, but especially for older children, it’s better to use height as a guide. Eight-year-olds can vary considerably in height, so it’s preferable to keep grade-schoolers in boosters until they’re 4’9”, which doesn’t always happen by age 8.

Children’s deaths from auto accidents dropped 45% between 1997 and 2009, but car crashes are still the leading cause of death for children ages 4 and older. And that’s not counting injuries: for every death, 18 children need to be hospitalized.

Nearly all parents have gotten the memo regarding the importance of car seat usage for infants; in 2008, restraint use for babies under 1 was 99%. For kids ages 1 to 3, the rate was 92%; it dropped to 89% for children ages 4 to 7. But the data includes any sort of restraint — car seat, booster or seat belt — and actual booster seat use for 4-to-7-year-olds was just 37% in 2007, according to the National Highway Transportation Safety Administration. (More on Time.com: Why the TV Is Risky for Kids: It’s Not Just the Programming)

Boosters are no less important than car seats, says Durbin. They lift a child up so that the seat belt fits the way it was designed to — low on the hips, with the shoulder strap crossing the middle of the shoulder and chest. To ride booster-free, older kids need to sit with their tush against the seatback, with their knees comfortably bent.

By the time kids enter grade school, plenty of children try to sweet-talk their parents into letting them not use a booster — “it’s so babyish,” is a common refrain — but parents should let them know that’s not an option (and it’s illegal).

“Negotiate with them over bedtime and broccoli, but don’t negotiate safety,” says Durbin.