UPDATED: Student Allegedly Involved with Teacher Brawl Pleads Not Guilty

• 2 counts of threatening a public school official
• 1 count of possession of a box cutter on school grounds
• 1 count of possession of less than 28.5 grams of marijuana on school grounds
• 1 count of force or violence against a school employee in retaliation for an act performed in the course of his or her duties

Teacher and coach Mark Black can be seen on cellphone video grappling with a student he had apparently confronted about having marijuana.

No punches were thrown, but Black can eventually be seen on the video with his arms locked around the student's legs, on the classroom floor. Some witness reports indicated the teacher had been stabbed with a pencil.

Black was placed on leave. Sandra Lyon, superintendent of the Santa Monica Malibu Unified School District, sent a letter home with students Friday saying "a number of videos capturing at least a portion of the incident are circulating, and I can tell you that what I witnessed on one of those videos is utterly alarming."

Based on what she had seen, the "physical restraint" used by Black was "unacceptable," Lyon wrote.

Lyon issued an apology over the weekend after supporters of Black accused her of rushing to judgment against the teacher. She issued a statement Monday insisting that placing Black on leave was a disciplinary act, but standard procedure.

"The district has launched an independent investigation into the events last Friday at Santa Monica High School," Lyon said. "That thorough, objective analysis will be done prior to the end of spring break. We urge everyone in our community to resist letting rumors and inflammatory statements shape their opinions. Only when all the evidence and witness statements have been reviewed will we have a true and accurate accounting of what actually happened."

--City News Service contributed to this report.