The fewer unknowns the better the data and the more accurate the experiment.<p>In terms of predicting how likely someone is to finish their freshman year of collage having a test where you can increase your score significantly with moderate levels of preparation is not a bad thing.  However, the fact you can easily game the test means it is a less accurate indicator of a student’s innate capability.  The fact you can retake the test creates yet another sort of bias. etc.<p>More generally, it's easy to focus on defects in the test, which are irrelevant in a larger contest <i>and</i> subject to change.