Here's a way to fire back. According to the College Board, nationwide, in order for students to have a 90% chance of passing the AP Statistics exam, they need to have a combined PSAT score (Critical Reading + Math) of about 135. Please see the following page for the verification of that number.
This was based on ALL AP exam takers for either 2006 or 2007. Obviously some students with CR+M above 135 don't pass the exam, and clearly some students with CR+M below 135 DO pass the exam... but on average your students should have 135. Note this is equivalent to about a score of 200 overall (CR + Writing + M), or an overall SAT score of about 2000 (getting close to Ivy League territory).
So, simply inform your administration that you will have a 90% pass rate as soon as they supply you with a classroom full of kids with 2000 on the SAT. If your district is anything like mine, there is maybe one or two 2000s at each school.
At my school, we are 84% free-reduced lunch, and VERY happy WHENEVER an AP subject has over a 50% pass rate. One of my friends who teaches a few miles away has VERY different demographics and 90% pass rate is expected.