A sixth-grade boy was attacked by three other students, one of whom choked him and threatened to crack his neck, during a P.E. class last Friday at Oak Grove Middle School in Concord, according to his mother.

The mother, who does not want to be named for fear of retaliation against her son, said she only found out when her son texted her from the school office saying he had been hurt, and she should come and pick him up.

Although the district and school have promised to discipline the students involved in the incident, the mother has filed a police report and is planning to remove her son from the school, saying some students are continuing to taunt him.

"These kids, little thug bullies, are threatening him," she said. "He's afraid. He's suffering through retaliatory actions now."

Principal Lisa Murphy Oates, who assumed leadership of the school this year, said at least one student is being disciplined.

"Bullying is not tolerated," she said. "Our entire goal is to have a very safe and secure school."

Concord police Lt. Garrett Voerge said officers were investigating the incident.

Voerge said one boy apparently kicked a ball that hit a teacher.

"The P.E. teacher was uninjured, and the three other students took issue with this, and it somehow resulted in a fight involving the three kids and the one kid," Voerge said.

Voerge said the school took immediate administrative action against two of the three students involved. Rose Lock, assistant superintendent for Student Achievement and School Support for the school district, sent the mother an email to assure her the principal was taking the incident seriously and taking appropriate action.

"I'm sorry you were not immediately notified," she wrote, "and will be working with the staff to review their communication protocol."

The boy's mother said she doesn't understand how her son could have been choked without the teacher noticing. She also said she should have been notified immediately by the school.

"If there is a district policy for no tolerance for bullying, then that needs to be implemented," she said. "It doesn't make sense to have it and not use it."