I am in Ashland, Wisconsin today and biking along the trail that circles the town. In a more isolated area of the trail I came upon a boy of about 12 or 13. I could see him from a distance. At first I saw him stopped, staring at his bike. The on his bike, pedaling backwards. Then off. I came up and asked if something was wrong with his bike. Yup. He was holding back the tears--he was several miles from home and his bike would not go forward. His chain was off track. I showed him how to put the chain back on but you still couldn't turn the crank. After staring at it for a while I saw that his rear wheel had come loose and was out of its mount. After a bunch of fussing I got his rear wheel on. Thankfully it had a quick release. I showed him how that worked and how it was important that the wheel be on the bike solid and that it should take some effort to move the quick release lever.
We ran through the gears and all worked well. He said thanks about a dozen times, got on his bike and blew past me for home. I wiped my incredibly greasy hands off on the grass and headed back to the motorhome.
Even though I am sure that I am preaching to the choir, parents need to teach their kids at least some basic things about how bikes work. His bike wasn't a POS, it was a Trek, a nice bike. But someone didn't put the wheel on properly and he had no idea about how a wheel goes on and no idea about how to put a chain back on.