A “strict” Colorado gym teacher is accused of assaulting a student — because the kid refused to stand for the Pledge of Allegiance.

Middle school teacher Karen Smith has been placed on paid administrative leave after the alleged incident at Angevine Middle School, school district officials said.

Local police confirmed to CBS in Denver that cops are investigating reports that Smith assaulted an unidentified student for refusing to stand for the Pledge.

No charges have been filed and details of the alleged incident had not been revealed by Saturday.

“I am reaching out to you tonight to let you know that we will have a substitute teacher working with some of our PE classes for the time being,” Principal Mike Medina said in a letter sent home to parents on Thursday night.

“While I cannot share much information, following an incident today at school, Ms. Smith was placed on paid administrative leave. We are working closely with our partners at the Lafayette Police department,” the letter read.

“We believe in due process and therefore ask that everyone respect Ms. Smith’s privacy at this time.”

Smith is a 20-year veteran at the school; she is known as a “strict” teacher, but that had never before been an issue, one parent of a child at the middle school told CBS.

It’s school district policy to allow students the choice of sitting or standing for the Pledge of Allegiance, a spokesman told The Denver Post.