He was the teacher slyly leaning against the classroom door as the morning bell rang; the one who knew everyone's nickname, after-school activities, and individual personality.

If he was demanding, it was only because Algebra and Calculus required focus. If an answer was wrong, he urged his pupil to rethink the question and try again. Nothing was free.

Then again, there weren't many easy answers in Jaime Escalante's classes. There couldn't be, under the guidance of a mathematician responsible for one of the nation's most successful Advanced Placement programs.

The United States Postal Service is honoring Escalante with a 2016 Forever postage stamp in homage of his work with inner-city students in Los Angeles between the mid-1970s and early 1990s. Among the reason they cited was how Escalante prove "that students judged to be 'unteachable' could master even the most difficult subject."

The Bolivia-born inspiration passed away in 2010, but his work lives on in every future engineer, architect, and accredited teacher who took his words to heart.

Escalante's Student, Now a School Principal, Talks to Latin Post

"Mr. Escalante dedicated his life to improving society as an educator," Elsa Bolado, one of Escalante's students and current principal at Graham Elementary in L.A., told Latin Post.

"To honor Mr. Escalante is to honor the thousands of anonymous educators in our public schools who generously give up precious personal time and resources, day in and day out, to ensure that students in socio-economically marginalized communities have the opportunity to pursue higher education and remain relevant."

One of Bolado's most vivid memories didn't involve a math book. It came when her Garfield High School classroom learned about their Latino roots, and how to find their own American Dream. Escalante said society would judge them by their name and color of skin, yet reaffirmed each and every student that they were "destined for greatness."

"He shared that we should be proud of our heritage, our language, and our parents," Bolado said.

Escalante's Humble Beginnings

Escalante immigrated to the U.S. in 1963, carrying about $3,000 and little else. Despite his lauded grasp of Calculus, the 33-year-old Bolivian worked odd jobs, including a stint in a coffee shop across the street from Pasadena City College. This is where Escalante would take English classes, and earn the associate's degree that led to a scholarship at Cal State Los Angeles.

Garfield High School offered Escalante his first teaching job in 1974. It was an arduous task in a troubled neighborhood known for crime. By 1982, his students were among the nation's best, defying perceived stereotypes by passing AP Calculus tests.

"Not until I got to UCLA did I understand how important and impactful Mr. Escalante's teachings were. It was almost as if he was predicting the future - we would be accused of cheating," Bolado said.

Educational Testing Services, the world's largest nonprofit testing organization, found that 18 students who passed the AP exam all missed the exact same question. Escalante questioned whether the decision to disqualify his students was racially motivated. Nevertheless, all but two of those who re-tested had their scores reinstated.

"Jaime Didn't Just Teach Math ... He Changed Lives"

Escalante would go on to see more of his students succeed - 73 passed the AP Calculus exam in 1987 - but it would be that 1982 group, the one that challenged misconceptions, that would be immortalized.

"Jaime didn't just teach math. Like all great teachers, he changed lives," said actor Edward James Olmos following his death in March 2010. Olmos, who portrayed Escalante in the 1988 film "Stand and Deliver," participated in a fundraiser to help pay mounting medical bills brought on by Escalante's bladder cancer.

"Stand and Deliver" was nationally recognized as a significant piece of American history, added to the National Film Registry in 2011.

Escalante's students found succeed beyond a letter grade. They found an identity; a way of looking at their lives with hope, belief, and a realistic possibility of reaching their goals. In that way, Escalante did change lives, one math problem at a time.

"Jaime Escalante dared to challenge the status quo. His achievements are not the result of magical teaching that transformed failing students into math savants," Bolado said. "Rather, he will always embody a maestro in the fundamental sense of the word: a composer capable of extricating hidden talent and nurturing the intrinsic motivation of the hundreds of students he taught."