A young boy wearing his Buzz Lightyear backpack races to class at New York School.

Kids have always been a pain. But these days, they’re also in pain.

“It’s an epidemic,” says Scott Bautch, a chiropractor specializing in occupational health and spokesman for the Arlington, Va.-based American Chiropractic Association. “By the age of 14, kids have the same rate of back pain that adults do.”

And Bautch thinks he’s fingered the culprit: backpacks loaded with jumbo textbooks. His young patients are often hauling around 30 percent of their body weight, and they have the hunched-over spines and tight necks to prove it. He says that number needs to be cut considerably — he recommends no more than 10 percent for kids under age 12 and just 15 percent for teens. Plus, he’d like to see them wearing better-designed bags.

Parents can help stem this surge of suffering by focusing on proper posture, says Esther Gokhale, author of “8 Steps to a Pain-Free Back” and creator of the Gokhale Method.

“There are kids who carry much heavier loads without wear and tear because they are well-aligned,” she says.

Avoid the calls to “stand up straight” and keep your “chin up, chest out.” Both can lead to further problems because they don’t really explain how to hold the body.

Instead, she prefers cues such as “have a ducky butt, not a tucky butt,” which is a cute way to help even elementary-schoolers get the right idea. “Imagine you have a tail. It should be out behind you. You don’t want to be sitting on it,” Gokhale says. She also likes to reminds children to “stack the blocks of the spine.”

The best prompts, however, are always the visual ones. “Kids model parents. If parents are slouching around, kids won’t know what to do,” she adds.

L. Cathy Mao, school nurse at Central Junior High School and Quail Run School in Lawrence, says that she rarely sees any students come in with complaints about back pain — at least not resulting from an overloaded backpack.

“It’s usually sports,” she says.

But after 20 years in school health, Mao says, it’s somewhat comforting that people are paying attention. Some students even use rolling versions of backpacks, like the carry-on luggage parents wheel through airports — on adorned with SpongeBob Squarepants or other characters popular with the youth set.

“It’s a good thing for people to be more alert,” she says. “When I was going to junior high, nobody was thinking about those sorts of things. It’s nice that people are paying attention to the weight of the backpacks, and how to carry it.”

Everyone needs to think about their core strength, because it’s those muscles that keep your middle from turning to mush, says Stephen Sarro, of Sports & Spinal Physical Therapy in Washington. He trains patients to find the transversus abdominis, the muscle that wraps around the torso, and then encourages them to keep that engaged during all exercises. (Gokhale has another cue for that one: “Imagine you’re reaching for something up on a high shelf.”)

Sarro also urges parents to notice how their kids hang out around the house. Sitting in front of computers placed on their desks is ergonomically sound, as long as their chairs have good back support. But teens are often typing away while laying on their bellies in bed. “Or, they’re leaning from the couch to the coffee table,” he adds. Positions like those can stress the spine and neck, too.

If you can manage to ditch the bulky backpacks and these bad habits, back-to-school season promises to be a lot less painful.