16-year-old high school student Gregory thinks of himself as a member of the "musical clique" at school and feels that the musicians are the best group of students. He thinks poorly of athletes and spends most of his time with peers who share similar interest. This is an example of theory.

Self-categorization

Explanation:

Based on the scenario being described within the question it can be said that this is an example of Self-categorization theory. This is a theory that describes  the different circumstances where an individual will perceive various individuals as a group, as well as how they are perceived. Which is what Gregory is doing by dividing the student population into groups and judging them based on different aspects.

the 5th amendment is about the justice system

explanation:

there is no double jeopardy

due process

grand jury

and that you can’t incriminate yourself