The students at Racine Lutheran High School posted pictures of the challenge onto a school-based Snapchat group, which involves one student kneeling on the other's neck.
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One parent, who asked not to be identified, said he's very disturbed.
"Are you kidding me? If you're in an open forum like that with all the students, that's a problem," he said.
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The parent said it's especially insensitive considering last month students, parents and activists publicly called out school leadership over what activists said were racially charged T-shirts some students wore to school. A swastika and the n-word were also found in a bathroom.
The school's principal emailed parents to say the students in the post were disciplined, but did not elaborate as to how.