REDWOOD CITY, Calif. -- A 34-year-old Petaluma high school teacher accused of setting up an illicit date with a person he believed was a 15-year-old girl pleaded not guilty in San Mateo County Superior Court Tuesday, a deputy district attorney said.

Scott Eugene Dietlin is charged with four felony counts of sexually explicit communication with a minor and faces up to five years in prison if convicted, Chief Deputy District Attorney Steve Wagstaffe said.

Dietlin was arrested in San Mateo on Nov. 22 after allegedly showing up for a date with "Jackie," a teenage persona created on MySpace by two teen boys, according to Wagstaffe.

The 15-year-old San Mateo County boys posted the online profile as a joke, Wagstaffe said. When Dietlin allegedly contacted "Jackie" in April, the boys initially played along, he said.

Over time, the communication included sexually explicit e-mails and text messages, police said. At one point, Dietlin allegedly sent "Jackie" a naked photo of himself, Wagstaffe said.

The boys finally decided to call police, Wagstaffe said.

Burlingame officers began posing as "Jackie" and set up a date at a location in San Mateo on Nov. 22, Wagstaffe said.

Dietlin showed up that morning and was taken into custody, police said.

Burlingame police searched Dietlin's car and Petaluma home, seizing items including condoms, a computer and a cell phone, police said.

Dietlin, who teaches world history and economics, has worked at Casa Grande High School for nine years, Superintendent Greta Viguie said.

His charges include sending harmful matter with intent to seduce a minor, sending harmful matter to a minor by use of email, communicating with a minor to set up a lewd act, and arranging a meeting for the purpose of engaging in a lewd act with a minor.

Dietlin remains in custody in lieu of $700,000 bail.