I think it's a California state test. So you could compare to a top school in a wealthy California suburb, but not to a school outside the state. I think.

Another thing is range. 10/10 is nice, but as you can see, a bunch of SF schools got it. Kind of how the Math GRE (used to?) top out at about 95%ile (ie., 5% of the people taking the test got an 800/800).

So this leaves open the possibility that even the best elementary schools are far behind the other 10/10s in other parts of the state. Kind of doubt it, since Lowell is clearly extremely competitive with top public and private high schools around the country. But I can't make the comparison directly at the elementary school level.

That's why I kind of put it as a question... what's your guess? Are the 10/10 elementary schools in SF notably worse than top elementary schools in Colorado? Like I said, I seriously doubt it, but I can't be sure.

It's almost certainly going to be whatever is the most prestigious or makes the school look the best. They'll obviously use national rankings if they're #9 in the nation. If they're #9 in Mississippi, they are probably not using national rankings.

I could be wrong but that's only a system that compares schools in CA with other schools in CA. It's currently being revamped so it may change.