I'm not pointing this out as a major gotcha, just something to be conscious of when you're reading claims about schools.
That said, here's Joanne Jacobs:
I met the dynamic Ali when she was recruiting students for KIPP Heartwood Academy, a public charter school in San Jose that ranks in the top 10 percent of California schools, despite its low-income, minority enrollment.
The rankings Jacobs refers to are based on growth, so in theory there is no particular disadvantage to starting with a low-income population and a potential advantage, as there is more space for growth if you start out behind. In practice, I'd guess that there is a very wide range of growth in low-income schools, moreso than in higher income schools. But overall, I'd expect the best low-income schools to look best overall in those rankings. Saying that they are highly ranked "despite" the population is a bit misleading.
People aren't used to thinking of "top ranked schools" in this way. Measured in terms of growth, the "best" school still might not be one that middle class parents would want to send their students to.