I think we should celebrate teachers like Mildred Grady who made an extra effort to help a child and encourage his interest in reading, and Olly Neal who succeeded under challenging circumstances. Both sound like exceptional human beings.
However, I think Kristof's column and the simple narrative that a single great teacher transformed the life of an "at-risk" youth and was the key factor that enabled him to become educated, get a law degree and eventually become a court judge, is somewhat misleading. The column obscures the other positive influences in Olly Neal's life that were probably as or more important than Mrs. Grady - parents, family, mentors, etc. In addition, it is unlikely that Mr. Neal would have succeeded if he didn't have many competent and caring teachers through his life - before and after Mrs. Grady - and access to functional education systems.
While a great teacher can make a difference with some troubled, surly kids in a high-poverty environment, the odds of this happening are very low struggling in many inner-city schools today. The schools with the most troubled kids in high-poverty environments tend to have the toughest working conditions, worst funding, and weakest leadership that few good teachers would want to work or stay at.