Well, you'd be mistaken. There are people who learn 3, heck, even 10 times faster than your standard bright university student, in large part because they needn't wait for formal instruction.
You have probably learned at this pace on certain topics.
Such people can defy the standardized logic of what's possible by a certain age.
For example, Howard Hughes:
Showing great aptitude in engineering at an early age, Hughes, Jr. built Houston's first "wireless" or radio transmitter when he was 11 years old.[5] He went on to be one of the first licensed ham radio operators in Houston, having the assigned callsign, W5CY (originally 5CY). [6] At 12, Hughes was photographed in the local newspaper, identified as being the first boy in Houston to have a "motorized" bicycle, which he had built himself from parts taken from his father's steam engine.[7] He was an indifferent student with a liking for mathematics, flying, and things mechanical, taking his first flying lesson at 14 and later auditing math and aeronautical engineering courses at Caltech.[5][7]
Philo T. Farnsworth:
Farnsworth excelled in chemistry and physics at Rigby High School. He asked his high school science teacher, Justin Tolman, for advice about an electronic television system he was contemplating. He provided the teacher with sketches and diagrams covering several blackboards to show how it might be accomplished electronically. He asked his teacher if he should go ahead with his ideas, and he was encouraged to do so.[13] One of the drawings he did on a blackboard for his chemistry teacher was recalled and reproduced for a patent interference case between Farnsworth and Radio Corporation of America (RCA).[14]