Marshon Sanders' mother wrote in an email to ABC7 that there were others dressed up as Mormons, priests and Moses without incident.
After initially sending the student home to change clothes, the school reversed its decision.
A statement from the school says:
"We initially were concerned that the costume could be offensive to religious sensibilities. Upon further review, we realized the student did not intend to be offensive. Therefore, the school communicated to the student that he could wear the costume.
"These were our Halloween costume guidelines shared with students prior to Halloween:
1. No head coverings, masks, or FULL face paint. We need to be able to identify students. (i.e. ghosts, masks from horror movies, etc.)
2. Costumes that are provocative, too revealing, or have questionable props will not be permitted. (i.e. "pimp", prostitute, props relating to tobacco/alcohol/drugs/sex, etc.) Costumes that do not meet our Personal Appearance guidelines (please refer to your student handbook, page 54) will not be permitted.
3. Costumes that could be offensive or perpetuate a stereotype of someone's culture, gender, sexual orientation, heritage or religion are not permitted.
4. Props such as weapons and inappropriate items will be confiscated. This includes props or make-up that suggests bodily harm. Please refer to your student handbook, page 38 for the school policy on school weapons.
Marshon's mother, Angenetta Frison, said she has taught her son to respect great people that and Jesus Christ is a great figure, adding there was nothing provocative or demeaning about the costume.
Frison said she was told some teachers found the costume offensive. The' costume included a long, white robe; red sash, head scarf and cross necklace.
Frison said she didn't question her son's choice of costume when he left for school.
"I encouraged him to dress as someone inspiring or uplifting," she said.
Melinda Vajdic, school spokeswoman, said the costume could be interpreted as poking fun or perpetuating a "religious stereotype."
"Costumes trivialize," Vajdic said. "I'm sure that wasn't his intent, but we want to maintain a culture of mutual respect."
Frison and her son are members of Jesus Name Apostolic Church in Waukegan. He also attends Willow Creek Community Church in Barrington.
Last Halloween, Sanders dressed as the rap artist formerly known as Snoop Dogg.
"They didn't have a problem with that," Frison said.
The Sun-Times Media Wire contributed to this report.