"Lacking a direct measure of aptitude, we link people to the mean combined SAT scores of their college and then divide them into six groups: those from colleges with SAT scores in the top five percentiles, the next 10, the next 15, the next 20, the next 25, and the bottom 25 percentiles. The SAT cut-points are constant over time so that aptitude is defined in absolute terms. The aptitude groups are finer at the top of the distribution because previous research suggests that the top quartile accounts disproportionately for the decline in teacher aptitude."
Whoever wrote this should lose their tenure immediately.
But what specifically are you disagreeing with in the paragraph you kindly quoted?
I'm not saying that it's impossible, but basing an entire paper on this premise without any supporting evidence is completely ridiculous. So far as I've seen there is zero evidence that this is true.
After some Googling, it seems that this measure of teacher quality is attributed to:
http://ideas.repec.org/a/ilr/articl/v55y2002i4p686-699.html
I don't have access to the paper, but from the summary I see no evidence that this measure has any empirical support.
See
http://learninfreedom.org/readseri.html
(I see the link began having DNS problems just as I posted it; it should be live later.)
for more about better reading instruction, and see
"Pulled Away or Pushed Out? Explaining the Decline of Teacher Aptitude in the United States" (American Economic Review, 2004)
for negative selection for academic ability in United States teacher training.