I finally found this about high school math classes taken in our district's middle schools:

The grade will be listed on the high school transcript under Grade 6, 7, and 8 with one unit of credit.

Only courses taken during the high school years will be included in the student’s grade point average.

In our case this is a good thing. DD is doing very well in all classes, but as DD is emotional, ADHD, and very young for middle school we could see things change. I don't want her grades received at age 10 to affect her college choices.