Saul Hillel Benjamin claims in a new lawsuit -- obtained by TMZ -- he was hired to run the Epiphany School for Global Studies founded by Sparks in 2006.

Benjamin says he began complaining to the author of "The Notebook" and others ... the school had virtually no African Americans -- 2 out of 514 students. Benjamin claims Sparks responded, "Black students are too poor and can't do the academic work."

Benjamin also says Sparks got incensed when he [Benjamin] met with the NAACP North Carolina chapter, telling the headmaster to "engage only in private and less visible contact with African Americans."

The lawsuit goes on ... claiming Sparks ignored bullying claims by gay students and even lent support to a student group that wanted to enact a "homo-caust."

Benjamin also claims Sparks publicly humiliated him by forcing him to get up in front of the entire school and justify his Jewish heritage. He says the parents of the students hurled insults at him while the board applauded.

Benjamin says he was fired and Sparks -- who famously wrote "The Notebook" about a couple's love transcending Alzheimer's -- telling others in the school to ignore Benjamin's claims because he was suffering from Alzheimer's.