Originally Posted by caedmyn
So how do you tell if a child is "develomentally ready" to sit in a booster seat?
Well, it's part maturity, and part parental discipline. I recommend parents of most neurotypical kids start booster training around 4 and 40. Start with short trips. Let them know that it's very important that they sit perfectly upright and not lean forward, bend over or slouch.
They can't reach to grab a fallen toy, play with or pull on the shoulder belt, turn around to look out the window or at somebody behind them, or scootch forward so that the lap belt isn't exactly where it's supposed to be.
Now, most kids will do these things naturally. The developmentally 'ready' part is, if you tell your child that they may NOT do these things, and they must sit up to protect their own safety, will they listen to you and do as they're told?
Most kids can understand the instructions and respond accordingly around the 5th to 6th birthdays (for full time use, not for occasional rides to get them used to using the booster).
Some kids cannot. Kids on the autism spectrum, kids with impulse control issues, kids with attention deficit issues, may have more difficulty (or may simply be incapable of) following instructions about using the booster.