He took a little piece of her heart.

Ex-Dallas Cowboys football coach Jimmy Johnson mercilessly bullied rockstar Janis Joplin and made her life “miserable” while they were students at the same Texas high school in the late 1950s, an upcoming book claims.

Johnson, now 76 and an analyst on Fox Sports, nicknamed the iconic singer “Beats Weeds” in a crude reference to her pubic hair, writes Holly George-Warren in her upcoming book “Janis: Her Life and Music,” according to the Daily Mail.

Hippy Joplin was an outsider at Thomas Jefferson High School with dreams of escaping tiny Port Arthur, Texas, and becoming a singer or painter.

Meanwhile, Johnson was the star linebacker on the Yellow Jackets, the school’s football team.

He and his jock crew allegedly groped Joplin and spread rumors that she’d slept with their friends because she “looked and acted weird,” the book claims.

By her senior year, the “Piece of My Heart” singer was “the image of everything the students disliked,” her friend Tary Owens told George-Warren.

“Janis looked and acted so weird that when we were around her, mostly in the hallways at school, we would give her a hard time,” he wrote.

She also reportedly “despised” sports — a big no-no in the Texas town.

Joplin’s reaction to the insults was to laugh them off, and the meatheads were never punished for their bullying.

Johnson went on to become a defensive lineman at the University of Arkansas — and then won two Super Bowls with the Dallas Cowboys as head coach from 1989 to 1993.

But he didn’t seem to let go of Joplin — who continued on her anti-establishment path, performing at Woodstock and becoming one of the most widely known rockstars of the 1960s.

In a 1992 Sports Illustrated interview, he claimed Joplin “never wore any panties,” adding “from what I understand.”

Joplin died of a heroin overdose at 27. She was inducted into the Rock and Roll Hall of Fame in 1995.

George-Warren’s book is out Oct. 22.