What are five movies based on discrimination?
Discrimination in terms of race, class and gender has been explored in many films over the years.
In fact, one of the staples of Film History courses famously deals with race and is now seen by many as a racist/discriminatory work. The Birth of a Nation by director D.W. Griffith depicts Civil War era Ku Klux Klan activities in the south.
"The Birth of a Nation, which is often considered the apotheosis of his technical achievement, can no longer be shown outside of academic settings because it is blatantly racist, depicting blacks as either buffoons or savages and the Ku Klux Klan as heroes." (eNotes)
While this film is hailed for its technical achievements (as one of the first feature-length narrative films ever made), it is also a source a controversy. Each of these facts make this a potentially rich film for inclusion in a paper on discrimination in films. There is no end to the material you will find in your research on The Birth of a Nation. (Yet, while the film certainly has a place in a conversation on racial discrimination, it may be better suited to a conversation more directly interested in racism.)
Other classic films also deal with discrimination. Charlie Chaplin's Modern Times explores issues of class discrimination in early 20th century America and Eisenstein's Battleship Potemkin also looks at class issues in Russia.
More contemporary films have taken discrimination as a central focus. Malcolm X, Selma and The Help are three films exploring racial discrimination and each approach the subject directly, though in different ways.
Girls Don't Cry examines gender and trans-sexual discrimination and The Color Purple looks at gender discrimination in a racially-specific context (in the American South).
With the exception of the Chaplin film listed, these films are often pointedly political and harsh. On a different note, the film Whale Rider functions as a commentary on gender discrimination within a New Zealand family and finds its way to an incredibly touching climax.
Depending on your specific approach to discrimination, you might also consider looking at Pretty Woman. This comedy-drama is known for its charms but the film's premise is built on discrimination relating to societal/moral biases against prostitutes. If this film fits into the scope of your essay, it might make an interesting counter-part to the more overtly political atmosphere of some of the other films (while also demonstrating the idea that popular films often have serious undertones).
You might consider doing a search for films of a certain type at a film database to get a list that specifically matches the ideas you have for your essay. The 1970s and 1980s were eras that generated many films about women in the work place and discrimination attached to that topic. The 1990s generated many films looking at race in contemporary America and sometimes in historical settings. (The big trials of the decade, with Rodney King and O.J. Simpson, kept race at the forefront of the national conversation.)
No list of films about discrimination would be complete without mentioning Spike Lee's Do the Right Thing. This film looks at discrimination as an active element of a 1989 Brooklyn neighborhood. (This is the second Spike Lee film on the list, but Lee has presented a continued dedication to this issue in his films since he began as a filmmaker in the 1980s.)