A Bronx middle-school teacher rattled her students — including one who was near tears — by showing an ISIS video of a terrorist beheading a journalist, documents show.

South Bronx Academy for Applied Media veteran Alexiss Nazario faced termination, but was let off with a $300 fine last summer after acknowledging she made a mistake by not previewing the clip or getting the principal’s permission.

Investigators spoke to three eighth-graders who were freaked out by the macabre clip, which showed a masked man holding a knife to the neck of a kneeling ­victim clad in orange.

The students testified that the video blacked out the actual beheading but showed its gruesome aftermath: the man’s severed head placed on top of his own chest.

“I’m scared at what I just saw. Ms. Nazario showed a beheading video and I was really scared,” one girl told a school staffer right after seeing the clip, according to an ­investigation by the Office of the Special Commissioner of Investigation.

“I don’t even watch scary videos at home,” the girl added.

Another student told probers he lost sleep the night after seeing the video, which had made him feel “uncomfortable.

“It was gross,” he said.

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