Police say David Considine, 47, went to a 7-Eleven on Madera Road wielding a knife and demanding money.
He was able to get away, but surveillance video of the suspect's car led investigators to him.
"One of the officers that saw the video tape saw the vehicle that matched the description. That's when the detectives got involved," said Lt. Mike King of the Simi Valley Police Department.
Simi Valley Unified School District officials have placed Considine on paid administrative leave during the criminal procedures.
"Should he be convicted, he will not be back," said Don Gaudioso, the district assistant superintendant. "Until that then, we've sent him a letter he's not to be on school grounds, school activities anything like that."
Considine's former students said he would tell them about his past trip to drug rehab.
"He told me it all starts as a small thing, but elevates to a bigger thing, so to just stay in school," said former student Jennifer Bueno.
"He would show up to school drunk and got really overweight and stuff," said another former student, Julia Anker. "It seemed like he was declining."