Tough-guy rapper Eminem was bullied so badly as a child his mother sued the Detroit school system for failing to protect him.



The torment of the then 9-year-old Marshall Mathers began on Oct. 15, 1981, when he was beset by a bully at the Dort Elementary School who split his lip and knocked the wind out of him, according to court papers unveiled Monday by the Smoking Gun website.



The bully, who caused Eminem to suffer from "nightmares and anti-social behavior," was identified in the papers as DeAngelo Bailey.



More beatings at the hands of Bailey followed, including one in a restroom that left young Marshall with "sustained injuries to his head, face, back and legs," the papers state.



On a snowy day in January 1982, Bailey nailed the future superstar in the face with a "snowball containing a heavy object or a piece of ice" while they were playing "King of the Hill" before beating him up, the papers state.



As a result of that attack, Eminem's mother, Debbie, claimed her son suffered a concussion and a temporary loss of vision in one eye.



Debbie Mathers Briggs' lawsuit for $10,000 in damage was eventually dismissed on the grounds of "governmental immunity," the Smoking Gun reported.



But Eminem got his revenge against Bailey in 1999, when he outed him as a bully in a rap song called "Brain Damage."



Some of the lyrics went:



"He banged my head against the urinal till he broke my nose/ Soaked my clothes in blood, grabbed me and choked my throat."



Bailey sued the rapper for violating his privacy in 2001 but admitted in interviews that he bullied Eminem. A judge later tossed Bailey's lawsuit and explained her ruling by writing a rap verse of her own:



"Bailey thinks he's entitled to some monetary gain/Because Eminem used his name in vain."



Now 38, Eminem has been speaking out about bullying amid a plague of suicides by kids who mostly got picked on for being gay. He also also been accused of fueling anti-gay bullying peppering his rap songs with slurs against homosexuals.



csiemaszko@nydailynews.com