A substitute teacher in California berated a 13-year-old student for wearing a pro-police mask, claiming the face covering was the new version of the Confederate flag, video shows.

Lucas Lillar was wearing the mask featuring a thin blue line in support of law enforcement when he was confronted by the educator last Monday in his math class at Lyman Gilmore Middle School in Grass Valley, Fox News reported.

“That’s not the American flag, that’s the new Confederacy flag,” the teacher could be heard saying in the video.

“Well, we can’t do the Confederate, but we can put up the red, white and blue. No, it’s black, white, with some blue line in it,” the substitute continued.

Lillar replied, “Yeah, it’s got the thin blue line.”

The teacher replied, “Yeah, but it’s not American.”

Lillar said he was scratching his head over the exchange, which he claims lasted 20 minutes.

“I was confused because I didn’t know what he was talking about at first. And then he kept saying that is un-American and how if police don’t like you, they’ll shoot you,” he told