In Kaffir Boy, track the changes in the main character's attitude about the day's events. How does his attitude change?

If you're referring to the day's events in Chapters 2 and 3, I would argue that the character's attitude changes from fear to hatred as the day progresses.
The events of the day began one cold morning in 1965. On that morning, the Peri-Urban police descended upon Mark's neighborhood in search of "people whose passbooks were not in order, gangsters, prostitutes, black families living illegally in the township, shebeen owners, and those persons deemed "undesirables" under the Influx Control Law." During such raids, Mark's parents usually hid away from home or made themselves scarce. Mark relates that he and his siblings were usually left to fend for themselves during such raids. 
His description of his feelings of terror and helplessness at being left alone are palpable. As the oldest, he was the only thing standing between the police force and his defenseless younger siblings. Added to his feelings of sheer trepidation were feelings of betrayal; his mother often left during Peri-Urban raids, causing Mark to question her love for him and his siblings. On that particular day, Mark was left alone to comfort his hysterical siblings; at only five years old, he sorely felt his lack of life experience during the entire horrific episode. Eventually, overwhelmed beyond endurance, Mark remembers covering his screaming infant brother with a blanket, not realizing that he might have suffocated George in the process.
Mark also slapped his sister, Florah, when she whimpered and screamed for their mother. He remembers that he desperately wanted to prevent the police from detecting their presence that day. As it stood, the police weren't interested in the children at all; they wanted to arrest all adults who were guilty of infractions under Alexandra's draconian laws. Mark's mother eventually returned after three hours, but Mark remembers cowering together with his siblings until she did so.
A little after midnight, the police returned. This time, Mark's mother hid in a wardrobe, while his father hid under a bed. Unfortunately for Mark, the police were not in a forgiving mood; they brutalized him with kicks until he bled and emptied his bladder in sheer terror and pain. His sister, Florah, was subjected to physical intimidation until she screamed uncontrollably. Mark reports watching as the police patronized and terrorized his usually bombastic father into submission. Accordingly, Mark's father had failed to pay both his poll and tribal taxes.
Worse of all, Mark's mother was nowhere to be seen, which meant that Mark's father had failed to adhere to the precepts that were put in place by the Peri-Urban force. As the police continued to intimidate Mark's father, Mark reports feeling an intense rage that frightened him to his core. His anger only intensified as he watched his father being led away in cuffs. So, on that day, Mark's attitude changed from acute fear to intense anger, due to the atrocities his people had to endure under the apartheid system.