Are you turning 18 soon? The last section on the link, above, says:

"If you are eligible as a child during the month before the month you attain age 18, we will redetermine whether you are disabled. When we do the disability redetermination, we will use the rules that we use for adults who are filing new applications for SSI."

It's a formality; depending on if you start working or going to college, etc., childhood issues can get better and not be permanent disabilities and they're just checking your progress. If you are getting better and they determine you could get a job (doing okay in college, say), that could make a difference or, if you are, like my friend, quadraplegic and obviously pretty wholly disabled (they paid for his training and he worked when he was able but because of his obvious disability, he was slower than others doing his job and during times of recession, like now, he'd be one of the first laid off; but, he's in his 50's now so getting of an age where the combination of age and disability makes it almost impossible for him to get a job so he's "permanently" disabled).