How did Ralph in his opening speech hope to motivate the boys to change their behavior? Why wasn't this strategy successful?

That afternoon, Ralph blows the conch shell and the assembly gathers. He begins the assembly seriously, telling them that they are there not for making jokes or for cleverness. He reminds them that everyone built the first shelter, which is the most sturdy, while the third one, built only by Simon and Ralph, is unstable. He admonishes them for not using the appropriate areas for the lavatory. Jack, however, uses the fear of the beast as to distract the boys and challenges Ralph's authority. The meeting falls to pieces.