I dropped out of high school and never set foot in a college classroom. What I have instead is something most credentialed educators cannot claim: I learned mathematics the hardest possible way, from first principles, entirely on my own, with nothing but time and the determination to understand — not just memorize.
Starting with Calculus I from a borrowed textbook, I worked forward through Calculus II, multivariable calculus, ordinary differential equations, linear algebra, statistics, and into abstract algebra — pausing to go back and fill gaps whenever the logic demanded it. I worked through Fraleigh's Abstract Algebra, Hildebrand's Numerical Analysis, Den Hartog's Mechanics, and university-level physics. Not cherry-picked. Cover to cover.
When I later took the GRE Math Subject Test — a exam designed for students finishing math undergraduate degrees, competing against seniors applying to PhD programs — I scored in the 35th–40th percentile cold, without review, years after last studying. That is not a credential. It is a data point that tells you where self-directed mastery lands against a formal university baseline.