The Battle Royale Act is a way for the government to control the population and keep people in line. By forcing students to kill each other, the government is sending the message that individuality is not tolerated and that conformity is essential. The students who are able to survive the Battle Royale are those who are willing to give up their individuality and conform to the government's wishes.
The novel is a powerful indictment of the dangers of conformity and a celebration of the importance of individuality. It is a story that will stay with you long after you finish it.