Johnson is now on paid administrative leave and in jail after police say she had a sexual relationship with a student.
"I saw it first on Facebook. So I saw what happened to Miss J.," said student Calvin Rasbold.
Students at Granada High call her "Miss J," but police are calling her a suspect in a sexual assault involving a student.
Johnson, 40, is a math teacher at Granada and she is also married.
"There's 24 counts that range from sexual intercourse with a minor, lewd acts with a minor, and oral copulation," said Livermore Police Officer Steve Goard.
The school called police on Tuesday saying a student had just told them about his relationship with Johnson that reportedly took place between December of 2010 and May 2011. The boy was 14 at the time.
"They met each other through social media, texting, Facebook, and then through Words With Friends' chatting option," said Goard.
Goard says the friendship led to a sexual relationship.
"That sexual relationship occurred inside her car and then throughout other different locations in Livermore, mainly in her car," said Goard.
The Livermore Valley Joint Unified School District released a statement saying the teacher had been placed on leave and that "the District [is] cooperating fully with law enforcement officials, while conducting a simultaneous personnel investigation."
A recorded message was also sent out to parents. It seems everyone at Granada High is talking about it and many are upset to hear of the allegations.
"Some of them are really coming to her defense who have had classes with her and who really like her, other kids are not being as nice," said Pam Rasbold, Calvin's mother.
Calvin didn't have Johnson as a teacher, but he did play Words With Friends with her, which is a Scrabble-type game that allows you to play other people through your phone or online.
"I've never played Words With Friends with any of my teachers except her, so like my relationship with her was like unique, it was like different. I talked to her like about other things, like she was kind of like a friend almost," said Calvin.
But Calvin didn't think much of it.
"She wants to get to know her students better. That's how I think of it," said Calvin.
Goard says parents need to be mindful of their child's social media relationships.
"For the most part, it's all appropriate, but some people take advantage of it," said Goard.
"It's never any kind of issue that has come to my attention before, worrying about a teacher being friends with a student on Facebook," said Diana Paynter. And when asked if she is now concerned, she said, "Oh yeah, for sure."
Johnson is scheduled to be in court on Friday. Her bail is set at $1.8 million. Livermore police say they don't have any indication at this point that there are any other victims out there, but they do want parents to sit down and talk with their kids. If parents have anything to add to this case, they should give Livermore police a call at (925) 294-7531.
Johnson's arrest is the fifth molestation case in the past five weeks in the Bay Area involving a school employee. The other defendants include a coach, two teachers, and a janitor.