Doctors and teachers say it's common for students to carry their backpacks with them in school throughout the day, but depending on how they carry their bags it may not be good for their back. At North Central Junior High in North Liberty, heavy backpacks aren't something students have to worry about. "One thing that we do to try to get out in front of that is we have a lot of online textbooks," said Principal Colby Miller. That's not the case for every school, which is why doctors are warning parents of the importance of buying the right backpack for their kids: one with two straps. "You don't want to wear just one strap because that could cause a different posture than you'd like," said Dr. Alex Riniker, a chiropractor at  Revive Family Chiropractic in Marion. Dr. Riniker sees kids of all ages come to his practice with their backpack loaded with books. He makes sure to tell parents it's important a bag doesn't weigh more than 15 percent of their child's weight. "If you think about a 50 pound child, 10-15 percent of that would be only five to 10 pounds or five to 12 pounds," said Dr. Riniker. Read the rest of the story here.