Another thing the city could do would be to use real IQ tests, which are more immune to the effects of prepping (how many numbers can you remember forwards? Backwards? Can you put the pictures in order to make a story? Here's a list of symbols and the letters they stand for. Now, solve the code below as fast as you can!)
Val
Actually, I believe that the test NYC uses, the ERB, is a close variant of the WPPSI. Some of the test prep companies advertise that they have actual test questions from the ERB. I do believe that you can train a higher IQ score into an individual by teaching them the actual questions on the test.
Someone else mentioned ability grouping. I am not too optimistic about that either, honestly, b/c a child in the top 1 or 2 percent of the population may not have any other kids of the same ability in his/her classroom. Kids in top 1% or above may not have anyone else with the same ability level in the whole bunch of classrooms in their grade or maybe even in the whole school.
I'm also not too sure that ability scores are fixed from one point to another. My mother recently offloaded a bunch of my old school papers to me. I came across a few "ability" tests I must have taken in elementary. I had no idea. We changed schools every year due to a lot of moving in my childhood so I was apparently tested on some things a few times. I have no idea what these tests were, but the grainy old computer print out of my ITBS or CTBS scores (achievement) on a few occassions also had a one liner that said "cognitive abilities" at the top. My scores on that ranged from the 84th once to the 99th twice. I had no idea that I had ever been below the upper 90s and am glad that that one score wasn't the thing that kept me out of GATE/GT programming in my childhood b/c the GT programs alone still weren't the best total solution for me.