The video appears to show a boy walk into a classroom at Rich Central High School in Olympia Fields and repeatedly punch a substitute teacher until he is restrained by classmates.
The teacher was not seriously hurt.
Police said several juveniles were taken into custody but no charges have been filed yet.
Rich Central High School officials said they are cooperating with police.
"We are disappointed as this goes against our efforts to ensure a safe learning environment for all students as well as staff. At this time, we are not able to provide additional comments due to it being a student discipline matter," said Rich Central High School Principal Todd Whitaker in a statement.
----------
* More local news
* Send us a news tip
* Download the abc7NY app for breaking news alerts