I will be happy to help you with the examples of prejudice in To Kill a Mockingbird, but you will have to organize your essay yourself.
THE JURY. Probably the most obvious example of racial prejudice in the novel comes the group of men who are sworn to uphold justice: the jury for the Tom Robinson trial. They apparently decide to honor a code that is more important in the Deep South of the 1930s: that a white man's word is always accepted over that of a black man. The jury disregardz the fact that Tom Robinson could not have used his left hand to strike Mayella, and that the left-handed Bob Ewell could. They believe the contradictory testimony of Bob and Mayella, and refuse to believe the more logical story as told by Tom. The author's purpose is to show that even a sworn jury will not accept the black man's word over that of a white man, no matter what the circumstances.
MISS GATES. Scout's teacher gives the class a good lecture about Hitler's persecution of the Jews, but Scout remembers a conversation she overheard that made her wonder about her teacher's true spirit.
"... Miss Gates... was talking with Miss Stephanie Crawford. I heard her say it's time somebody taught 'em a lesson, they were gettin' way above themselves, an' the next thing they think they can marry us. Jem, how can you hate Hitler so bad an' then turn around and be so ugly about folks right at home--"
Harper Lee shows us just how strong the hatred of the black man runs in Maycomb. According to Miss Gates, Jews are worthy of pity, but black people are not.
AUNT ALEXANDRA. When Auntie tells Scout that she cannot invite Walter Cunningham Jr. to the Finches' house
"Because--he--is--trash, that's why you can't play with him."
Alexandra displays her special type of prejudice: social bias. More than anyone else in the story, Alexandra believes that her own "high breeding" sets her apart from most other people in the town.