[Before] DON'T LOAD THEM DOWN. Limit a pack's weight to no more than one-quarter of a child's body weight. For a 70-pound kid, that's about 18 pounds. There are points of honor to consider, however, so let them pack their own clothes and sleeping bags. Knowing that they're carrying their own weight, so to speak, gives them an incentive to work through the inherent discomfort of backpacking.