ROCKVILLE, Md. — Once a week, for a few hours after school — and when the courthouse is otherwise quiet — the teenagers take over.

Role-playing as lawyers, bailiffs and jurors, and with help from volunteer lawyers and judges, the teenagers mete out justice in “Teen Court.”

Teen Court gives some first-time juvenile offenders the chance to avoid juvenile court and instead face a jury of their teenage peers.

The diversion program is celebrating its 20th year in Montgomery County.

All public and private high schools participate in it.

Over the past two decades, more than 5,000 cases have been heard in Teen Court. Besides diverting first-time offenders from the criminal judicial system, Teen Court gives inquisitive high school students the chance to learn about law and to rub elbows with legal professionals.

“Ladies and gentlemen of the jury, please stand and raise your right hand,” intones the teenage bailiff, with a teen offender in the dock and a dozen teens in the juror’s box.

A lawyer who rushed over to Circuit Court from her private practice fulfilled the role of judge in the case of a teen charged with heisting a case of beer.

“Everybody’s here because I think they really think they’re doing something good for young kids in our community, in giving them a different way out of the problems that brought them into the criminal justice system,” said John McCarthy, Montgomery County state’s attorney.

Mary Leseur, a 17-year-old junior at Holton Arms School, served on a jury which peppered a defendant with tough questions about the theft of a cellphone and credit card from a classroom.

“We really want to know what’s in their mind when they commit a crime. We want to get to the bottom of it, and I think one part of it is asking the important questions,” said Leseur. “I’m interested in a career in law, so this has been a really interesting opportunity.”

Students receive student service learning hours for their participation, and it’s open to all high school students who live in the county.