A former Napa math teacher has been sentenced to seven years and four months in prison for committing sexual acts with an under age boy in Sonoma County.Josefat Estrada Jr., 35, pleaded no contest to oral copulation with a victim incapable of resisting the act and two counts of oral copulation with a person under age 18.The incidents occurred in the Sonoma area between 2005 and 2007 and were reported to Sonoma police on June 25, 2008, the Sonoma County Sheriff’s Department said. Estrada was arrested at his Napa home on Nov. 16, 2008.None of the incidents occurred while Estrada was teaching at the school and the boy was not a student there. The victim was 14 when the sexual conduct began and Estrada was a trusted friend of the victim’s family, investigators said. Estrada was charged with eight counts of oral copulation of a minor, oral copulation of a minor unconscious of the act and one count of committing a lewd act on a child. Seven of the counts were dismissed at sentencing Thursday in Sonoma County Superior Court.Deputy District Attorney Tashawn Sanders said there was only one victim.Sharyn Lindsey, assistant superintendent of human resources of the Napa Unified School District, said in November that Estrada taught math at Vintage High School since the fall of 2005 and previously taught math and health at a secondary school in New York City between September 2003 and June 2004. He was placed on unpaid leave after his arrest.