The boy's father, Robert Casteel, said his son, Christopher, told him a boy at school pulled a knife on him and threatened to kill him.
"I said, 'What? Did you tell the teacher, the principal?' And he said it was in class," Casteel said.
The boys are fourth graders at Mission Bell Elementary School in Jurupa Valley.
"He said, 'I'm going to get you after school," Christopher said, adding that the boy flashed the knife underneath his desk.
Casteel said he took out the temporary restraining order after learning that the boy was only given a five-day suspension.
Deputies, who Casteel called to investigate the matter, found a 2 1/2-inch pocket knife on the boy while he was at school.
Casteel is citing California's education code, which calls for the expulsion of a student caught carrying a weapon on campus.
"I knew he was going to come back, but I thought they should expel him because my dad said in the rule book that knives and guns were not allowed," Christopher Casteel said. "They should be expelled."
Jurupa Unified School District would not comment on the incident because of privacy issues, but said the situation was investigated and handled properly.
"It's a very unusual situation we find ourselves in," said Tamara Elzig, the school district's assistant superintendent for personnel services. "It's our understanding that we do not have enforcement authority regarding that restraining order. However, we will cooperate with the courts and with law enforcement."
Under the protection order, the alleged bully, who has since been taken out of Mission Bell by his mother, has been told to stay 20 feet away from Christopher Casteel and his two younger siblings.
Robert Casteel said he is doing what is best to protect his son.
"I don't feel like I am overreacting," he said. "I feel like it could have been a different situation. What if the kid would have actually stabbed my son?"
The restraining order will remain in effect until Feb. 8 when the Casteels go to court, where a judge will determined whether a longer-lasting restraining order should be issued.