When your kid is first beginning to scooter, he will probably start out on a Razor A1, A2, A3, B model, Pro model, or similar folding aluminum scooter with adjustable handlebars. These work decently for younger riders when they are first starting out, but once your scooter kid is good enough to tailwhip or if he weighs more than about 60 pounds, then it's time to start considering purchasing a better quality scooter. That's a general guideline, but I'll go into more detail as to why you should upgrade your kid's scooter.
There is no actual designation for different levels of scooters, but for the sake of this article, I'd like to explain the delineations I see in scooters. These are by no means industry standard divisions. These are just how I envision the various types and levels of scooters on the market today.