Joannie's teacher saw from day one how smart Joannie was and knew the girl belonged in an honor class. The class transfer could easily have been arranged, but Joannie's teacher decided to stay mum on her ability. You see, the teacher knew he would be judged by his passing statistics and by the number of kids who scored over 90 on the upcoming regents. The teacher knew there were weak students in the class and Joannie's presence was needed to keep those numbers up. Besides, moving Joannie up would mean a seat would be opened for a lower performing student who would lower those numbers.
Joannie suffered because the teacher's supervisor cared only about numbers. The teacher knew from experience that the members of his department were constantly being measured against one another and while he wanted to do what was best for Joannie, he had to do what was best for him. He had seen the wrath of the supervisor and it was something he wanted to avoid.
Until things change, until statistics stop meaning so much and until supervisors like the one above cease to exist, kids like Joannie will continue to be sacrificed daily. And the sad thing is, no one seems to care.