One hypothesis is that Jeb Bush's A-F system is a simple and easy to understand method with easy to interpret results. But this is Florida mixed in with some educrats, sooo....
The system isn't as complicated as I thought (see for yourself here), but there are some oddities. For example, most people probably think "90+%" when they hear "A." For Florida, it's 70% (1120/1600) or better. So a large block for "A" schools. It gets weirder: a B has a range of 65%-70% (1050-1119). A 5% range for B's? Here's the whole shebang:
(All scores out of 1600)
A: 1120+ (70%, range of 30%)
B: 1040-1119 (65%-70%, range of 5%)
C: 880-1039 (55%-65%, range of 10%)
D: 800-879 (50%-55%, range of 5%)
F: <800 (below 50%, range of 50%)
It seems like they're trying to use a standard curve (1600 a la the SAT) and the traditional A-F, but not unsurprisingly, failing at both. But this isn't even the worst part--it's how they arbitrarily shift the numbers they use in the calculations around. For example, a week ago
"Education Commissioner Pam Stewart said a key reason for the drop in
A-rated schools was that the grading formula was changed to make it more
difficult to earn a top grade."
Now rewind two years:
"State education officials panicked, and at an emergency meeting last
week, the Florida Board of Education decided in a 4-3 vote that the best
thing to do was to lower the passing score on this exam.
Let me repeat that: In order to make sure that students succeeded on the test, the passing grade was lowered."
So, when it comes down to it, all the math, all the calculations mean nothing--the numbers are fudged to whatever looks or feels "right" to the powers that be. Once again, the math is just there to provide a false sense of credibility.