GRASS VALLEY (CBS13) – A middle school student said a substitute teacher provoked a verbal altercation over the image of the “Thin Blue Line” flag on a mask he wore in class.

It happened at Lyman Gilmore Middle School in Grass Valley and was filmed on cellphones by multiple students in the classroom on Monday.

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According to 13-year-old Lucas Lillar, he was in math class working when the substitute teacher sat at an empty desk behind him and began to provoke an argument over the image on his mask.

Lucas shows the mask he was wearing in class.

The “Thin Blue Line” flag resembles the American flag, but has a blue stripe, which is a sign of support for law enforcement. Recently, it has come to represent opposition to the racial justice movement. 

Lillar, whose father and stepmother are members of law enforcement, said he wears the mask as a show of support for his family.

“It just makes me feel worried,” he said when asked about what it is like to be the son of a member of law enforcement.

The “Thin Blue Line” flag, which resembles an American flag but has a blue stripe, is a sign of support for law enforcement but has also come to signal opposition to the racial justice movement and a symbol of white supremacy or support for the Blue Lives Matter cause.

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In videos obtained by CBS13, the substitute teacher compares the flag to the Confederate Flag. In one instance the substitute teacher said, “That’s not the American flag that’s the new confederacy flag.”

Watch the extended interview below with Lucas and his mother

“I was extremely angry and heartbroken, that this…that he had to deal with it,” said Amanda McCallum, Lucas’s mother. 

McCallum said she went school administrators when she learned about the incident. She said she was told by Lyman Gilmore’s Principal that the substitute teacher will not be able to teach at the school in the future.

“I never had someone talk to me like that, yell at me in my face, especially a teacher,” said Lillar. 

Andrew Withers, the Grass Valley School District Superintendent told CBS13 in an email that the incident at Lyman Gilmore Middle School is currently being investigated. He wrote that he cannot comment further on personnel matters. He also wrote:

The California Education Code §44953 allows for the immediate dismissal of a substitute teacher. Our district expects all educators to perform their duties with utmost respect and professionalism.

Scott W. Lay, the Nevada County Superintendent of Schools, told CBS in an email he refers back to the district where the incident took place and cannot comment on personnel matters. He wrote:

The incident is currently under investigation, and we will take appropriate action. The California Education Code §44953 allows for immediate dismissal of a substitute teacher. We expect all educators to perform their duties with utmost respect and professionalism to afford our youth an environment conducive to learning. The California Commission on Teacher Credentialing that governs educator credentials will be informed of this incident.

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McCallum said she hopes to meet with the superintendent next week.