Calculating a School's Peer Group in NYC

Here's the formula that NYC uses to define similar elementary schools demographically in their progress reports:

( % eligible for free lunch x 30 ) + ( % students with disabilities x 30 ) +
( % Black/Hispanic x 30 ) + ( % English language learners x 10 ) = PEER INDEX

So, for example, a school with 65% poverty and 95% black/hispanic is considered to have equivalently "high needs" as a school with 95% poverty and 65% black/hispanic. I know which one I think would be easier to get high test scores out of. To take a less realistic example (the first is based on Harlem Success Academy 1 and its closest peer) I'd take 100% black/hispanic with 0% poverty over the inverse any day of the week.

Or what about 60% black/hispanic and 0% ELL vs 40% black/hispanic and 60% ELL? Equivalent?

Of course there is no right answer and the main point that all these scientific numbers involve quite a bit of guesswork. Embedded in here, however, is a strong statement about the extent of the presumed disadvantage of race. It is, the NYC school district is telling us, as powerful a force as poverty, a diagnosed learning disability, and much worse than not speaking the language well.

Later... it would be interesting to see how the ratings would change if you multiplied these instead of adding.