Yes Kriston! The current measurements of gaps are flawed - your idea of pre-testing makes so much sense. The standardized tests should also have a broader range to measure progress at both ends of ability.

According to some data (sent a link on another thread), advanced kids have been making "less" gains on a yearly basis than average kids in school under NCLB - so you could say that there is an achievement gap - gifted children achieve less from baseline over the course of the year!