Mennonites - similar to the Amish but drive cars. They do resist pop culture's influence and maintain dress and mannerisms consistent with their religion.
Buddhist monks - committed to a life of isolation and reflection, they stay true to their beliefs and free from pop culture by simply living separately from it.
Catholic nuns (to some degree) - who take a vow of poverty, live in a sisterhood, forego sex and marriage, and avoid what they would consider the sinful side of popular culture.
What a great question for a ninth grader! I rate your question 5 stars.
1. Orthodox Jews. They were able to keep popular culture out through socialization that surrounds their religion.
2. Fundamentalist Islam was able to keep out popular culture due to religion. Also they draw a strict boundary on ethics. And if they follow the five tenets of Islam with zeal, then this separate them as well.
3. Some ethnic minorities that have come to live in different countries due to language barriers and a "ghetto" mentality.
For a good book on this, see: A Rumor Angel by Peter Berger.
- Taliban -- Afghanistan. Resisted modern popular culture by coercing people who did not agree with them. They gained control of government and used their power to enforce their resistance.
- Amish -- United States. Resist the use of technology. They are able to do this through religious faith and indoctrination.
- Mormons -- United States and throughout the world. Resist aspects of popular culture that they think are sinful. They do this by religious teaching and by peer pressure, I guess you could call it, execept in a good way.
So the two that have managed it without violence or coercion do it through religious faith.