Could someone answer this question please. How can stereotyping affect group relations?

Your school subject is obviously not "college."

Stereotyping assigns negative (and occasionally positive) traits to all members of a group that is different than yours.

How would these stereotypes affect group relations?

Mexicans are lazy.
Blacks are criminals.
Whites are out to get us.
Asians are smart.
Rednecks are ignorant.
Irish are drunks.
Rich are stuck up.
Muslims are terrorists.