Hi,

In my experience, those tests are fairly accurate. I've had a couple students score well above or well below their practice tests, but mostly, I'd say they are accurate within about 50 points (warning: based on unscientific, anecdotal evidence).

In other words, if you're scoring in the mid-500s on those tests in an accurate test taking environment, I wouldn't go in expecting a 700 (or, on the brighter side, a 400 either). But, a 600 is certainly attainable.

Good luck!