How does the 'unnoted' pupil present a contrast to others?

Directions: Read the given extract to attempt questions that follow:    

The tall girl with her weighed-down head.    
The paper-seeming boy, with rat's eyes.    
The stunted, unlucky heir of twisted bones, reciting a father's gnarled disease,    
His lesson, from his desk. At back of the dim class    
One unnoted, sweet and young.    
His eyes live in a dream…