A former Montgomery County music teacher was indicted Thursday on 39 criminal counts related to his alleged sexual abuse of 14 elementary school girls and rape of a middle school student during his lengthy career in the county’s public school system.

Lawrence W. Joynes, 55, faces the possibility of decades in prison if convicted of all the charges, which include sexual abuse of a minor, child abuse, second-degree rape and other offenses related to sexual conduct.

Joynes has been in jail since his arrest a year ago in Baltimore County for possession of child pornography. He was recently sentenced for that offense — to time already served, or about a year — and was transferred to Montgomery for prosecution on the abuse allegations. He is being held without bond.

Thursday’s indictment roughly doubled the number of charges against Joynes since he was first accused of abuses in Montgomery in August.

The teacher worked the last 10 years of his 27-year career at New Hampshire Estates Elementary School in Silver Spring, where police say most of the 14 children he allegedly abused were in kindergarten to second grade. The alleged offenses date from 2005 to last year, and he taught at the school until his arrest.

Lawrence Joynes (Baltimore County Police)

Joynes was originally charged with a count of sexual abuse of a minor for each elementary school child. The indictment also includes individual counts of permitting a minor to engage in a representation of sexual conduct. Court papers allege that Joynes posed the girls in sexually suggestive ways, having them suck on his finger or a peppermint stick, while he recorded and photographed them. A number of the backgrounds appeared to be of a classroom, the papers say.

Police alleged that Joynes captioned some of the students’ images with fantasies of molestation, and they said in court papers that Joynes got a tattoo on his shoulder bearing the name of one of the victims.

In late 2011, Joynes — while still teaching — was instructed not to touch children, be alone with them or sit with them in the cafeteria, according to court papers. But the documents indicate that one kindergartner’s alleged abuse happened while Joynes was on restriction.

Investigators say that Joynes had the confidence of many students and parents and some members of the administration.

“That worked to his advantage at New Hampshire Estates,” said Capt. Bob Carter, commander of the Montgomery police department’s family crimes unit. Carter said that Joynes used his artistic talents to take advantage of his students: “He used music to open the hearts and minds of these children.”

Joynes’s alleged crimes began long before his years at New Hampshire Estates, court papers say. A grand jury in Montgomery returned second-degree rape, sex-offense and child-abuse indictments in connection with his time teaching at Eastern Middle School in Silver Spring in the early 1990s. Joynes allegedly earned a student’s trust and increasingly pressured her into sexual activities, a number of them while they were inside the school. At least once, he allegedly videotaped himself sexually abusing the girl, according to police.

Thursday’s indictment increases to 10 the number of criminal counts Joynes faces in the former middle school student’s case, including separate episodes of sexual conduct.

Alan Drew, an attorney for Joynes, could not be reached Thursday. Contacted earlier this month, he declined to comment on the case.

Montgomery schools officials issued a statement Thursday calling the allegations “very disturbing” and saying that they have cooperated with the investigation and will continue to do so.