How Good a Predictor of an ACT score is the Red Act Book?

If a student consistently scores a 33 while taken the practices tests in the Red Book (real world conditions, timed, etc.) how likely is that to actually translate into a 33 on the real test? Just wondering if anyone has any insight into that?

Personally, I averaged a 34 in the red book and scored a 36 on the actual test. For many, however, the red book is easier than the actual test. I think it was easier for me on test day because I was “in the zone” and it was my last chance. The red book has a different reading section (no double passage), which may harm or help you. Also, the science does not always have a conflicting viewpoint passage
Hope this helped. Thanks!

was pretty accurate for me except for math which I scored 4 points lower on the actual test than what I was getting in the red book