Spending per pupil can be a deceiving statistic due to the vastly different needs between poor/middle-class/wealthy students
I would suggest that the students here are doing well due to a combo of the following factors:
Smart parents live here, and they have smart kids
Rich parents spend less time fretting about paying bills and more time helping kids with homework
One (rich) parent works, one stay-at-home parent takes care of the home -> more time with the kids
One parent is involved with the PTA, which correlates well with student success
And to he clear, I'm not casting judgment. I live in Frisco, Tx. We are enjoying ALL of the above benefits
Well educated parents are more likely to have the skills themselves to help with homework and are more likely to put more emphasis on academic performance.