Of all the riveting stories that made up Muhammad Ali's amazing and controversial life, the most intriguing to me is how well he performed despite testing poorly in school.

Conventional measures of intelligence did not capture his potential, but he did not let that stop him. He didn't sulk, pout or give up. He tried harder. Having his abilities underestimated by others only seemed to make him more determined.

In his Louisville high school, young Cassius Marcellus Clay Jr. -- Ali's original pre- Muslim "slave name"--had such poor grades in the tenth grade that he had to drop out and repeat the year, according to David Remnick, editor of The New Yorker and author of the "King of the World: Muhammad Ali and the Rise of an American Hero."

When Ali later took the Selective Service's mental aptitude test in 1964, the year of his first heavyweight championship at age 22, he scored only between the 16th and 18th percentile.

That was well below the required minimum of the 30th percentile -- until the Pentagon lowered the requirement to the 15th percentile in early 1966, making him draft eligible. "I said I was the greatest," he famously quipped at the time, "not the smartest."

FBI director J. Edgar Hoover apparently wanted to make sure Ali hadn't deliberately gotten a low score. According to "Muhammad Ali: A Biography" by Anthony O. Edmonds, Hoover assigned an FBI agent to check on Ali's draft status the day after he announced he had converted to Islam and joined the black separatist group Nation of Islam.

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"The fact that Cassius barely earned a certificate of attendance and scored 83 on an IQ test administered by the Army," Edmonds wrote about the FBI's findings, "seemed to validate its decision."

Yet George Foreman and Earnie Shavers, among other boxers that he beat, said he was one of the smartest boxers of all time and had a keen ability to con his opponents.

That wasn't just boxer talk. Ali was a well-known rule breaker. He liked to thrill crowds with his swift scissor-step shuffle. He would drop his hands, hold his chin up, lean straight back and commit other no-no's to avoid a punch and taunt his opponents.

Ali also was "hyperverbal," Remnick reports in The New Yorker, which a fancy word for a kid who talks a lot, a characteristic that fed right into Ali's penchant for poetry, an unusual pastime for any boxer but particularly fruitful for Ali.

In his autobiography "The Greatest: My Own Story," written with Chicago writer Richard Durham and edited by Nobel and Pulitzer-winning author Toni Morrison, he fondly recalls reading poetry at the Bitter End café in New York's Greenwich Village, where he met an African-American poet he had long admired, Langston Hughes.

Ali praised Hughes' classic "I, Too, Sing America" and asked Hughes "if he had any more," Ali recounted. Hughes responded by giving Ali three books of his poetry. "His were the kind of poems I liked," Ali wrote. "Straight, simple, and at least half of them were in rhyme."

They also helped Ali's poetry, loaded as it was with rhyme, braggadocio and swagger, to launch the first glimmers what we later would know as hip-hop. An art form that, like it or not, has changed the music world from the Sugar Hill Gang to the hit Broadway musical "Hamilton."

Ali was the first hip-hop heavyweight, whether he knew it or not. He fascinated, enraged or bemused us (take your pick) because he had to do things his own way, even when it meant risking his personal freedom by refusing induction into the Army in 1967.

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Still, contrary to those who call him a "draft dodger," he didn't dodge anything. He thought long and hard before he refused the draft on religious grounds and took his punishment.

He was convicted and stripped of his boxing titles and banned from fighting for 3 1/2 years at the peak of his abilities. Only a Supreme Court ruling kept him out of prison and overturned his conviction.

With that, Ali made many of us rethink the war, the draft and a lot of other sticky issues.

If his earlier militancy -- often delivered with charming wit -- seemed to mellow in his later years, it was largely because the world had changed, too, even as he helped to change it.