The incident took place at Mmametlhake High School premises in Mpumalanga on Thursday.
The incident was captured on video and has been shared on social media.
In the video, the former learner can be seen throwing bricks at some of the windows of the school, when the police arrived on the scene.
The learner then started throwing bricks at police, leading to officers shooting him in the leg.
Watch the video by clicking here: