Joan Clemons has twice undergone back surgery, which makes her sensitive to the possibility that toting heavy textbooks around school all day could be detrimental to her son Robbie. "My son is perfectly healthy," she says, "but when I saw what he was carrying to middle school, I got concerned about his back." So Clemons joined forces with other parents, teachers and administrators at Robbie's school in Sharon, Massachusetts, to alleviate the backpack burden on kids.

The school's Backpack Committee persuaded a private company to donate some binders, which they were able to sell in turn to parents. The proceeds were enough to buy extra copies of many of the textbooks used at the school, allowing kids to store one copy of each book at home and have another waiting for them in the classroom. That cut Robbie's backpack weight from 30 pounds to about 15 pounds worth of binders and gym clothes.

It was one small step, but it's more than most other schools have done to lift some of the weight off students. Textbooks have gotten bigger and heavier, while many schools do not allow students access to lockers because of safety and drug concerns. It has all added up to a daily load for middle and high school students that might strain a seasoned backcountry hiker.

"We do have research in children and adults that once you've hurt your back, you're at a higher risk for injury," says Shelley Goodgold, a professor of physical therapy at Simmons College. Goodgold readily acknowledges that there haven't been long-term studies that show direct evidence linking backpack weight to serious injuries and long- term problems in children. But she has done a study of 345 Boston-area students that found 68 percent of sixth graders were carrying more than 15 percent of their own body weight on their backs. That's the limit recommended by the American Chiropractic Association and other health groups.

New Jersey state Representative Peter Barnes recently introduced legislation that would limit elementary and secondary textbook weights, saying that students today are carrying bigger backpacks than he once did in the Army. California state Representative Rod Pacheco, swayed by the burden on his own children, introduced similar legislation to limit textbook weight in his state. Although Pacheco's bill was watered down, the state Assembly did vote nearly unanimously in May to require the state Board of Education to survey all school districts to see how they are dealing with the weight issue and require the state Department of Education to present some potential solutions. (Last year, Pacheco got $100,000 in funding for a study through the California legislature, but Governor Gray Davis vetoed it.)

There aren't any obvious solutions to the backpack weight dilemma. Many schools can't afford duplicate textbooks, which can cost more than $10,000 at even a small institution. Replacing books with lighter CD-ROMs would also be expensive, especially when you factor in the necessary computer costs. Some schools have pushed for backpacks on wheels, but those cause congestion in the hallways, aren't useful where there are stairs and are almost universally dismissed by older kids as hopelessly dorky.

Indeed, fashion pressures pose real problems for juvenile backpack- wearers, from their penchant for slinging packs over one shoulder to the loose-strap look that pulls weight away from the back and ruins posture. A teacher at Sharon Middle School came up with the idea of featuring some of the most popular kids on posters demonstrating proper and improper ways to wear backpacks. That had some effect, but since Robbie Clemons has moved on to Sharon High School, his load has grown heavier again. The school has smaller lockers, short breaks between classes that are widely spread out, and different levels of instruction taught within each grade, making textbook duplication prohibitively expensive.

What's more, high school kids aren't interested in wearing their backpacks in any ergonomically correct way. "A lot of the kids have this fad where they wear it all the way down to their tush there," Joan Clemons laments.