Our tests are not 80 points below, according to our internal numbers; the GMAT estimator is based, at least in part, on old CD tests that we no longer use because they are inaccurate, and I just had a student get a 780 on a diagnostic meaning that he would expect an 860 on the real thing

As for where it will take you, well as I said, every point counts. Our course is comprehensive, building on foundations of algebra and subject-verb agreement up to complex concepts like combinatorics and past perfect tenses. I've had students enter advanced classes with a 600 and leave with a 700; I've had at least one enter in the low 700's and leave with a perfect scores. Our materials are highly personalized, and I'm sure we'll be able to make them fit you.