A Vintage High School math teacher has been arrested and charged with child molestation.

Josefat (Joe) Estrada, 35, who lives in Sonoma County, was arrested this weekend in Napa on 18 separate counts involving lewd acts with a child under 18.

He is being held in the Sonoma County jail on $250,000 bail. Estrada and the boy believed to be his victim know one another, police said. The boy is not a Vintage student, according to police.

Estrada has been a teacher at Vintage since 2005, according to Vintage High School Principal Eric Schneider.

“I received a phone call on Sunday about Joe’s arrest. This is a very sad and devastating day for Vintage,” Schneider said Monday morning.

“I am sure the first concern parents who are hearing about this is, ‘does it involve any of our students?’” Schneider said. “I want to make it very clear that this tragic incident does not involve anyone (attending) our high school.”

Estrada is originally from Tempe, Ariz., Schneider said.

“He taught in Tempe, and then in New York City, where he was before he came to Napa,” Schneider said. “This is just devastating for us. He had a huge impact on the school. In addition to his math teaching assignment, he was also involved in the freshman transition program. This is a significant loss for the school.”

Police say the sexual encounters began when the boy, who is now 18, was 14. They continued for about two years, according to Sonoma County Sheriff’s Sgt. Glenn Lawrence. “A family member came forward and reported the alleged crimes,” Lawrence said.

Estrada was a trusted friend to the family of the teen, according to press release from the Sonoma County Sheriff’s Department.

Estrada is scheduled to be arraigned in Sonoma County Superior Court today at 8:30 a.m.

Correction: An earlier version of this article misspelled Mr. Estrada's first name