Sheriff Dozier found out professor Tolson was the "ringleader" (the one trying to organize a union for sharecroppers and laborers) by beating up Samuel, a sharecropper.
Samuel had been present on the secret meeting aimed to organize a union for sharecroppers lead by professor Tolson disguised as a sharecropper.
"The great debaters" is a 2007 drama, directed by Denzel Washington. Based on the true story of Melvin B. Tolson, a professor at Wiley College Texas who inspired students to form the school's first debate team and went on to challenge Harvard in the national championship.
An exam invigilator, exam proctor or exam supervisor is someone who is appointed by the examination board and services for maintaining the proper conduct of a particular examination in accordance with the exam regulations.
The function of the commas in this sentance is to seperate the thoughts, one being "Isn't it fanciful notion that any adult could actually understand teenager's mind?" and "As our parents always said"