I am working on teaching JB (5) as Eden describes. His bike has coaster brakes so we had to be careful of hills because he couldn't stop without pedals. We're up to pedals back on, seat high enough to pedal comfortably yet still touch the ground easily, and a bar I've attached to the back so I can hold the bike while he pedals. I only keep him from crashing, he has to balance and, unless he's going to get hurt, stop himself. He's gotten to where I can take my hands off the bar (but keep them close to grab it when needed) for several seconds. Usually he doesn't even notice I'm not hanging on. It's going ok.
I used to have an open mind but my brains kept falling out.