I agree with the point made earlier that achievement test results are only a function of exposure. I think that they are very unfair.
A very bright kid that hasn't been exposed (for socio-ecomonic or any other reasons) is unfairly dinged by them in my opinion. It also allows not so bright kids whose parents have deep pockets to prep the bejeesus out of them so that they just squeeze over the GT bar.
All in all they seem to stack the deck against kids from less affluent families getting public GT places - the very places that ought to be helping them overcome their less privileged backgrounds.
