I'm guessing that most of the children that were on the blog as sex offenders were for kiddie porn. The law does not differentiate between the ages of people other than those who are in the photographs. This is a very good thing, because it allows for the ability to push kids who are 'sexually abusing' others by passing around photos and what not from sexual harassment to child pornography charges.
The boy highlighted at the top was convicted of "lewd conduct" (basically, touching designed to arouse himself, the other person, or a hird party) with another under-sixteen-year-old.
The rest, it doesn't say. And the problem is that the law as written does not distinguish between two fifteen year olds doing a little through-the-clothes touching and the fifteen year old physically molesting an unwilling five year old. Both are technically the same offence.
I also suspect that aside from the knowledge of the convicted offense, the records are sealed for pretty much all these cases, so knowing whether these kids are harmless technical offenders or scary sociopaths is pretty much impossible.
I think some would presume that they tend more towards the latter and that prosecutions would not go forward unless the underlying actions were toward the worse end of the possible scale, but I've seen some things of how the criminal justice system works, and read about a whole lot more, and you can't guarantee that.
It only requires one out of three of the following for prosecution even in one of those more minor cases: a very angry parent of the other kid (especially if they're well-off or otherwise influential), a zealous prosecutor, or a kid whose family don't have the money (or don't care) to get him proper defense counsel. If two out of three are the case, he's in trouble.
As to statistics; the stats that are being thrown around in here are, I'm sure, for adult sex offenders, and thus don't really shed much light on any of this for the specific case of people who get convicted of possibly consensual sex crimes when they are themselves children.
It deeply disturbs me that we have laws on the books that could send a fifteen year old to jail "up to life" for consensual making out with someone else the same age.
It also disturbs me that we have a system where he is then classified the same as someone who did something much worse.
It's also bad in the sense that if the sex offender registry is increasingly used for very minor crimes, that its utility is diminished. Do they really want a situation where people think that everyone so registered probably just urinated in public or had a seventeen-year-old girlfriend when they were eighteen?
Because that's the ultimate end result. And as more people hear about cases when minor things got someone forced to register as a sex offender, the more it'll happen, and the more that the actual bad people this is supposed to protect against will be able to claim that actually they hadn't done anything all that bad, "did you hear about that guy on the news who has to register as a sex offender for public urination? That's about what I'm on there for ..."