BRIDGEPORT Cell phone video obtained by News 8 shows a grown man standing over a seventh grader and slamming a ball down on the student's head.
Bridgeport ISD confirms the incident happened at its middle school last Thursday during a gym class.
The district said the substitute teacher was promptly removed from campus and that the student is okay.
But the 14-year-old's mother is still visibly upset and shaken. Her son is in remission from leukemia.
"The substitutes... they're supposed to be people you can trust," she told News 8.
On the video recorded by another student, a game of dodgeball is being played when it appears to spiral out of control.
The teacher who the district said substituted occasionally during the past few years is seen suddenly grabbing a basketball and slamming it down on the teen's head. He then says something to the effect of, "You want to be down there crying like he is?"
News 8 isn't naming the 65-year-old man because he hasn't been officially charged or arrested.
Bridgeport police are investigating and expect to make a decision on charges shortly.
The district said it is still trying to determine what led up to the incident, but said that under no circumstances would the teacher in question be allowed to return to the classroom.