Images have emerged showing a security guard unconscious on the floor after he was knocked out by a teenager at a school struggling with discipline.

Alphonso Stevenson, a 63-year-old conflict resolution specialist hired to quell the violence at Bartram High School in Philadelphia, was allegedly assaulted by a 17-year-old student on March 21.

Stevenson was greeting students as they walked to class when the teenager knocked his clipboard from his hands, and when Stevenson went to reach it, the boy allegedly pushed him against a wall.

The staff member’s head smashed against a wall, knocking him unconscious and leaving him with a fractured skull, concussion and other injuries, the Philadelphia Inquirer reported