The woman in this video is Science teacher Sheri Lynn Davis, 40, a mother of two boys ages 4 and 14.
She is facing an unrelated criminal charge in which she is accused of slashing the tires of another woman's car with a knife in January 2009, the Associated Press reported.
In this video shot on April 29th, she is seen attacking 13-year-old Isaiah Reagins at Jamie's House Charter School, a Houston-area alternative school.
Davis' attorney, Chip Lewis, said a fight in the hallway that was not related to Davis' duties started the sequence of events.
"She saw no one was addressing the fight, she went with another teacher to break it up," Lewis said. While she was in the hall, she heard her classroom door "not only shut, but lock."
"And that's when a sense of panic came over Miss Davis," Lewis said, adding that among the students behind the locked door was a female "special needs child."
He said Davis shook the door until she caught the attention of a student who opened it, and then came the beating. Here is the AP story.