I just referenced the letter we got when DD tested into this class, and it's actually quite clear. It says her 7th and 8th grade grades in math will be entered into her "permanent" high school GPA, though this still confuses me a bit--I guess she just will have more high school grades to average than other kids? It is actually a bit of a "scare" letter, direly worded, and I hesitated to put her in this class, even though she tested in easily. I posted about it here when making the decision, in fact.

In my district, AFAIK, you may not take this class without meeting two bars (standardized test score bar--easy--and placement test--harder).