Sonya Carson decided to take matters into her own hands by switching off the television. Ben and Curtis were allowed to watch only two programs a week, and their mother made them read two books each week from the Detroit Public Library. The boys were also required to write book reports, which Sonya would underline and mark up. Only later did Ben Carson realize his mother, who had left school after the third grade, was barely able to read. "She pulled a fast one on us," Carson told David Gergen of PBS, "but after a while, something happened. I began to actually enjoy reading the books.... I could go anywhere in the world, be anybody, do anything. You know my imagination began to run wild." Within a year-and-a-half Carson went from the bottom of his class to the top of his class.
What does the red sentence mean?
She fooled them. Although the mother could barely read, she was able to convince her sons to read. They didn't know of her limited literacy at the time.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.