A 41-year-old D.C. public school teacher has been charged with having sex with a 13-year-old girl in what authorities say was one of several sexual encounters he had with the junior high school student.

Ricardo Roberts, a social studies teacher and basketball coach at J.H. Johnson Junior High School in Southeast Washington, was charged with first-degree child sex abuse after he was arrested last month at his Alexandria home.

He is being held without bond. School officials said he has been suspended from his job.

In charging documents filed after his arrest and in testimony yesterday in D.C. Superior Court, police said Roberts not only had sex with the girl in a classroom but also took her to his home and had sex with her there.

The alleged relationship came to light last month after a witness working in the school after hours Dec. 4 reported seeing the girl emerge from a room where Roberts had been seen changing his clothes a short time earlier, according to the charging papers.

The girl allegedly told a witness that she was in a sexual relationship with Roberts, and that led to a police investigation.

The charging documents gave this chronology of events:

When first interviewed Dec. 19, the girl denied that she and Roberts had sex. She acknowledged that there was talk around the school that she and Roberts were intimate, a rumor she attributed to her reputation for promiscuity.

Interviewed by police the same day at the school at 1400 Bruce Place SE, Roberts denied having a relationship with the girl. He, too, acknowledged rumors of a sexual relationship and, as the girl had, said such rumors were fueled by the girl's reputation for promiscuity, the documents said.

When the girl's mother learned of the investigation, she told police that she did not believe her daughter's account and brought her back to police for more questioning. In that interview, the girl said she had lied the day before because she didn't want to hurt "Coach Rob," who was her volleyball coach and social studies and homeroom teacher last year. She told detectives that between September and December, she and Roberts had sex several times, including two days earlier, on Dec. 18, at Roberts's home, the charging papers stated.

Arguing before Judge Lee F. Satterfield, Roberts's attorney, Kelli Neptune, assailed the credibility of the government's case.

But the prosecutor, Assistant U.S. Attorney Mark O'Brien, said that the witness statements corroborated key elements of the girl's account and that the girl was able to describe in detail the interior of the defendant's home.

The judge found a basis to proceed with the charge against Roberts, whose pregnant wife was in the courtroom yesterday, surrounded by relatives.

Staff writer V. Dion Haynes contributed to this report.