How do the main characters grow in Lord of the Flies as the story progresses?
To properly address how the characters 'grow' in Lord of the Flies, I think that we need to define what particular kind of growth we are looking for. Certainly all of the characters experience change while on the island, but not all of them necessarily 'grow,' because the word 'grow' implies some sort of improvement. My first impulse would be to say that Roger and Jack do not grow at all, but rather digress in terms of character and moral fortitude, but you could also make the argument that they grow in other less desirable ways. Jack grows in his ability to kill and use intimidation and violence against others; he increases his skill as a hunter as well as his capacity for commanding respect and fear. Roger also demonstrates growth, but in a purely malevolent, evil fashion; he grows from being a schoolyard bully to a full-on sadistic torturer of other small children.
The boys who show genuine growth in character are Piggy and Ralph. Both are hardened by their experiences on the island and learn to become physically tougher. Piggy is forced to adapt to life with only 'one good eye' after his glasses are broken and learns to live with his asthma, even pitching in to help with firewood after Jack leaves the tribe. Ralph grows up on the island as well and in the end, "wept for the end of innocence" (202). Circumstances and his role as chief made him take responsibility for the littluns; he built huts and tried desperately to maintain the signal fire so he and the other boys could be rescued.
All of the characters grow and change throughout the course of the novel, but Ralph probably demonstrates the most growth and improvement of all the bigguns; he stays true to his moral and social beliefs, firmly refusing to be dragged down to the savagery of the hunters.