Knockout (2011)

Dan Barnes (Steve Austin) is a former pro boxer who retired after growing weary of his violent existence. Now a school janitor, Dan tries to help a new student, Matthew Miller (Daniel Magder), who is being targeted by bullies.

While Matthew learns how to box and stand up to his tormentors, one of whom is the school boxing champ (Jaren Brandt Bartlett), Dan's new found role as a teacher helps him come to terms with his tumultuous past.