Standardized testing is not a great equalizer. It is a great way to maintain the status quo though. Paying for GRE classes can raise your GRE scores. Historically, IQ tests have "proven" that whites are smarter than other races.
Why the scare quotes? On average, whites score a standard deviation higher than blacks on IQ tests, and East Asians score half a standard deviation higher than whites. IQ is strongly heritable (0.5-0.8) and is strongly correlated with lifespan and income.
These are facts. They do not disappear merely because they disagree with your worldview. If you start with an incorrect premise, there's no limit to how wrong your conclusions can be.
Let me be very clear. When I was 15 I took the SAT and got every single question right. That was undoubtedly in part because a) I grew up in one of the wealthiest counties in the country b) my parents got me private math tutoring from the time I was 7 c) they read to me from an early age d) they sent me to private school e) I could go on, but you get the point. If you do well on these tests, good for you! But the idea that they are unaffected by confounding factors like income, education, and stereotype threat is absurd. These false beliefs that we can just give people a test to measure true talent worry me in light of Silicon Valley's incredible lack of diversity.
If IQ tests worked as you described, then in studies of twins going adopted into different households, we should see life outcomes correlated more with foster family than with each other. It turns out that twin life outcomes are very closely correlated with each other and strongly with IQ tests than they are to rearing family.
Your beliefs are the ones that are false, sorry.