Very true, indigo. Almost everything is vulnerable to a certain amount of manipulation by the motivated stakeholder--some less legal than others, some merely ethically questionable.
I speculate that the author's interest in NWEA MAP instead of ISEE is related to this point, since, unlike ISEE, there is not exactly a thriving test-prep industry around MAP, and the adaptive nature of the test (including a fairly deep pool of equivalenced test items) ought, in theory, to make it a bit more challenging to game.
In addition, since in many places it is routinely administered district-wide, 1-3 times annually, it may be viewed as possibly more accessible to a wider range of the school population. It even comes in Spanish.
In no way am I proposing it as a be-all, end-all, (especially since MAP was originally designed for lower-stakes progress monitoring, rather than high-stakes access to services) but I think it's valuable that something like this is in the conversation regarding access/selection to advanced learning opportunities, especially as, with reference to the quote, nationally-normed testing (or even psychometrically sound state-wide testing) is one of the few objective measures that cannot be heavily bent by the personal biases of teacher, parent or administrator (assuming ethical administration and scoring).
