The Bethesda subdivision of $600,000 townhouses and leafy courtyards is a tranquil counterpoint to the brutality alleged to have occurred there this month: the sexual assault of an "adult entertainer" by three Walt Whitman High School students who police said lured her to the house with an offer to make an adult video.

Montgomery County police said the three students -- ages 14, 15 and 19 -- skipped class on the morning of Nov. 8 and lured a 25-year-old woman from an escort service to one of the students' homes in Bethesda. When the woman arrived, they beat her with a baseball bat, attempted to cover her mouth with a cloth that emitted a "medicinal odor," then sexually assaulted her with the bat and another object, police said.

Ryan Howard Baird, 14, of the 12200 block of Village Square Terrace in Rockville, was arrested at school Friday and charged as an adult with first-degree sex offense, conspiracy to commit first-degree sex offense and armed robbery.

Also charged as adults with multiple counts of robbery and assault are Andrew Geoffrey Klepper, 15, and Young Jiung Song, 19. One law enforcement source said yesterday that Klepper was charged as an adult because of the violent nature of the attack and the role that authorities believe he played in it.

Police said the students got the woman's number from an Internet ad and told her they were adult video producers who wanted to offer her a job. When the woman entered Klepper's mother's residence shortly before noon, police said, the three students hit her in the head with a bat, tried to put the cloth to her mouth, took her cell phone and keys and threatened her with a knife. They proceeded to sexually assault her with the bat and another object, police and prosecutors said.

Police said that the woman called to report the attack at 5 p.m. that day. She was treated at Shady Grove Adventist Hospital and released.

Authorities said they believe Klepper placed the phone call inviting the woman to his home. The woman described the house and items inside it to investigators, police said.

Klepper, a sophomore, was charged with first-degree sex offense, conspiracy to commit a first-degree sex offense, armed robbery and conspiracy to commit armed robbery. People at his house declined to speak with a reporter yesterday.

Song, a senior who lives in Cabin John, was charged with armed robbery, conspiracy to commit armed robbery and first-degree assault. His family could not be located for comment yesterday. Klepper and Song spent Thursday night in the county jail.

Klepper's parents posted $50,000 cash bond, and he was released Friday on the condition that he stay away from the woman. Song remains in jail, and his bond review is scheduled for Monday. Baird was being held last night at the Montgomery County Detention Center.

Paul F. Kemp, the attorney for Klepper, declined to discuss the charges yesterday but said he will seek to have his client tried in juvenile court.

"The case really deserves to be there," he said.

Kemp said he would file a waiver seeking to have the case returned to juvenile court after the indictment is handed up, likely next month. The request will trigger an investigation by the Department of Juvenile Justice, which considers the nature of the crime and the defendant's age, mental and physical condition and his amenability to treatment.

A hearing on the issue is likely in February, Kemp said.

The residential development where the alleged crime occurred is tucked off River Road in Bethesda just north of the Capital Beltway.

News of the charges was slow to circulate through the school system after police announced the arrests Friday. Several students and teachers at the Bethesda school hadn't heard of the incident when contacted yesterday.

"I've gotten a couple calls, and I'm sure the parents are very concerned," said Lafe Solomon, co-president of the school's Parent Teacher Association. "I think they all realize it's a horrific incident, but it's also isolated."

Song was listed in last year's yearbook as a member of the Korea Club. Klepper transferred to Whitman this year, according to a teacher.

Klepper had tried out for a school production of the musical "42nd Street," which is scheduled to debut this week.

"He originally was cast -- he made the ensemble -- but then he decided not to do it," said Chris Kosmaceski, a music teacher at Whitman.

Staff researchers Madonna Lebling and Margaret Smith contributed to this report.