Conflicts between nationalities and between different socio-economic groups are historic. Ponyboy, who narrates the novel describes his situation:
We're poorer than the Socs and the middle class. I reckon we're wilder, too. Not like the Socs, who jump greasers and wreck houses and throw beer blasts for kicks, and get editorials in the paper for being a public disgrace one day and an asset to society the next. Greasers are almost like hoods; we steal things and drive old souped-up cars and hold up gas stations and have a gang fight once in a while.
In conflict theory, it is often the case that the upper class wishes to maintain its superiority, so it attacks in some way any one who attempts to invade its territory. With the Greasers, there is a camaraderie that offers emotional support that may be lacking in the boys' respective homes. On the other hand, the Socs lead comfortable lives and join together for the thrills of fighting and doing mischief. In Chapter 2 Ponyboy remarks that he was assigned Great Expectations to read for his English class,
...and that kid Pip, he reminded me of us--- the way he felt marked lousy because he wasn't a gentleman or anything, and the way that girl kept looking down on him.
With inferiority complexes, the Greasers feel a need to prove themselves, while the Socs defend their higher social status. In addition, they often try to eliminate any competition they may have for girls, territory, etc. These two elements enter into the main conflict between the two groups.