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.