The brother and sister-in-law of former first lady Michelle Obama have taken legal action against a private school over the expulsion of their children, the New York Post reported. Craig Robinson and his wife, Kelly, believe the University School of Milwaukee booted their sons following their complaints about racial bias in the curriculum.

According to the outlet, the Robinsons reported concerns about “the repeated use of racial and ethnic stereotypes” in their children’s homework assignments, particularly during their virtual learning sessions.

“Just as recent as 10 years ago, the University School of Milwaukee had in their fourth-grade curriculum that students reenacted the Underground Railroad, and students dressed up as slaves and ran through the school in the dark, and the teachers were actually the slave masters who captured these students,” Kelly told ABC. “​O​ne of the other stories that we heard was about how the ​Black students seem to get more harsh punishments than their white counterparts​.”

The private school, Craig added, also used the word “plantation” and additionally displayed “an insensitivity to socioeconomic status and as well as a disregard for the children who weren’t physically in the classroom​.

The Robinsons claim their complaints were succeeded by the expulsion of their 11 and 9-year-old, who were kicked out of USM in April and June, respectively. They believe the school is “retaliating against them because of the issues we brought up” and are suing them for breach of contract and racial discrimination — an act they believe will “help all students at the University School of Milwaukee.”

The school has since denied the allegations, explaining that the kids were expelled because the Robinsons had “not fulfilled the foregoing commitments as a partner to USM and its Middle School teachers and administrators.”

See a clip from the Robinsons’ “Good Morning America” interview below.