You also have to account for racial/cultural,
  language, and income bias

Whatever backlash Amazon faces for asking for overall average SAT scores, it's nothing compared to the backlash they'd get if they'd asked for average SAT scores for white and asian kids from married two-parent families with a six-figure household income, english as a first language and both parents college graduates.

They probably wouldn't need to ask for this. They can just combine public data sets with the SAT scores to come up with a rough, adjusted estimate.

But that's assuming they'd even want to correct for any of the aforementioned biases. I doubt they care because their employees wouldn't care. "Good school" in some places often also means "white school" because of the nature of income disparities, but you never hear parents asking, "But when you say 'good,' are you adjusting for race?"

Unpopular truth... but most companies (and people) looking for places to move to will, in reality, factor those biases into their decision rather than correct them out.

Who honestly ever says, "Oh, this location is fantastic... as long as you close your eyes and imagine a completely different population living there!"? There are many moral considerations to argue, but raw outcomes do usually prevail.

Except I wouldn't call that a bias. Bias is prejudice, and in this case would mean something like hiring people for certain characteristics that are irrelevant w.r.t. to the job. Even where ethnicity and race are concerned, it doesn't necessarily imply bias. If, say, a black social organization only hired black people, it wouldn't necessarily be biased. Why on earth would they hire, say, white people?

If you were starting a company and you wanted to attract people that value education and want the best for their children and see SAT scores as an indicator of quality, then yeah, you'd do exactly something like this. There's nothing immoral about it, unless you want to debate the effect Amazon will have on the town. What's immoral is the weird guilt and self-flagellation involved in thinking there's anything wrong with it. Who gains exactly from plopping Amazon HQ2 in some shitty town?

If there's anything I worry about, it's the growth of Amazon and its bed fellows.

The gap between SAT/ACT is really important. In my state, SAT scores are actually really high - but it's only because almost everyone takes the ACT and the SAT is only taken by elite people.

Your comment is very on point. The situation where more elite students take certain tests makes it much harder to understand skills and achievements that come from different schools.