The school district says the purpose of the assignment is to help students develop critical thinking skills, and debate whether the Holocaust was a "propaganda tool that was used for political and monetary gain."
"It's not a debate, you know, historians all agree the Holocaust is historical fact," said Matthew Friedman of the Anti-Defamation League.
The organization says the idea of Holocaust denial can be addressed in schools, but calls this assignment the wrong way to do it.
"To have students try and determine whether or not it happened, they're gonna go online and they're going to Google the Holocaust and come across sites that look very slick and very persuasive, but are really bad history and propaganda for anti-Semites, and that's not what we want them to be doing," said Friedman.
The Rialto Unified School District released the following statement: "Our Interim Superintendent will be talking with our Educational Services Department to assure that any references to the Holocaust 'not occurring' will be stricken on any current or future argumentative research assignments. The Holocaust should be taught in classrooms with sensitivity and profound consideration to the victims who endured the atrocities committed."
A spokeswoman says the district takes issues of intolerance very seriously. She also said the district made plans three months ago to have a group of students visit the Museum of Tolerance in June.