It should be approximately ten thoughtful pages long. Please note that in all written work, grammar, spelling, organization and structure are important and will affect your grade. If I can't understand you, I can't appreciate the genius of your argument. Write and proofread carefully. And, as ever, do your own work, and footnote every idea that is not your own.
Plagiarism is a serious offense.
I mean this. Ida B. Wells, Crusade for Justice William Chafe, Civilities and Civil Rights Stephen Whitfield, Death in the Delta Greenberg, ed., A Circle of Trust Barnard, ed. Read them for a sense of how a test works, what testers do, what they look for, questions they ask. You need not follow every detail or memorize statistical results. Racial Matters , chaps.