JENA, La. (AP) — Thousands of chanting demonstrators filled the streets of this little Louisiana town Thursday in a massive show of support for six black teenagers initially charged with attempted murder in the beating of a white classmate.

Throngs of black-clad protesters jammed the grounds of the local courthouse and a nearby park while thousands more marched along city streets in what at times took on the atmosphere of a giant festival — with people setting up tables of food and some dancing to the beat of a man playing a drum.

The crowd broke into chants of ‘‘Free the Jena Six’’ as the Rev. Al Sharpton arrived at the local courthouse with family members of the arrested teens.

Martin Luther King III, son of the slain civil rights leader, said the scene was reminiscent of earlier civil rights struggles. He said punishment of some sort may be in order for the six defendants, but ‘‘the justice system isn’t applied the same to all crimes and all people.’’

The six teens were charged amid racial tensions that had been growing after the local prosecutor declined to charge three white teens who hung nooses in a tree on their high school grounds. Five of the black teens were initially charged with attempted murder in the December beating, but that charge was reduced to battery for all but one, who has yet to be arraigned; the sixth was charged as a juvenile.

‘‘This is the most blatant example of disparity in the justice system that we’ve seen,’’ Sharpton told CBS’s ‘‘The Early Show’’ before arriving in Jena. ‘‘You can’t have two standards of justice.’’

‘‘We didn’t bring race into it,’’ he said. ‘‘Those that hung the nooses brought the race into it.’’

Sharpton, who helped organized the rally, said this could be the beginning of the 21st century’s civil rights movement, one that would challenge disparities in the justice system.

The district attorney who is prosecution the teens, Reed Walters, denied on Wednesday that racism was involved in the charges.

He said he didn’t charge the white students accused of hanging the nooses because he could find no Louisiana law under which they could be charged. In the beating case, he said, four of the defendants were of adult age under Louisiana law and the only juvenile charged as an adult, Mychal Bell, had a prior criminal record.

‘‘It is not and never has been about race,’’ Walters said. ‘‘It is about finding justice for an innocent victim and holding people accountable for their actions.’’

The beating victim, Justin Barker, was knocked unconscious, his face badly swollen and bloodied, though he was able to attend a school function later that night.

Bell, 16 at the time of the attack, is the only one of the ‘‘Jena Six’’ to be tried so far. He was convicted on an aggravated second-degree battery count that could have sent him to prison for 15 years, but the conviction was overturned last week when a state appeals court said he should not have beens ahead even after the conviction was thrown out. Bell remains jailed while prosecutors prepare an appeal. He has been unable to meet the $90,000 bond.

‘‘We all have family members about the age of these guys. We said it could have been one of them. We wanted to try to do something,’’ said Angela Merrick, 36, who drove with three friends from Atlanta to protest the treatment of the teens.

The Rev. Jesse Jackson spoke to a crowd Thursday morning. Dennis Courtland Hayes, interim president and CEO of the NAACP, compared the outcry over the Jena arrests to the controversy that followed racial remarks by radio personality Don Imus.

‘‘People are saying, ‘That’s enough, and we’re not taking it any more,’’’ Hayes said.

The rally was heavily promoted on black Web sites, blogs, radio and publications. State police declined to give crowd estimates, but participants at the park and the courthouse appeared to number in the thousands.

Sharpton admonished the demonstrators to remain peaceful, and there were no reports of trouble as of midmorning. Many white residents in the predominantly white town of 3,000 have complained that the town was being unfairly portrayed as racist.

‘‘This doesn’t offend me. I’m glad they’re doing it. I believe in people standing up for what’s right,’’ one white resident, Ricky Coleman, 46, said as he watched the rallies. ‘‘What bothers me is this town being labeled racist. I’m not racist.’’

‘‘I don’t think these folks have a clue what’s happened here,’’ said Kenny Robertson, 50. ‘‘This is a good town. I was born and raised here. We’re not racists,’’ Robertson said. ‘‘When all you foreigners get out of here, things will go back to normal.’’

A group of about a dozen white residents and black demonstrators engaged in an animated but not angry exchange during the march. Whites asked blacks if they were aware of Bell’s criminal record, blacks replying that Jena High School administrators had mishandled the incidents at the school.

Another white resident, Bill Williamson, 59, said he spent much of the morning trying to convince black visitors that the town was being treated unfairly and that Mychal Bell belongs in jail. ‘‘I think we changed one man’s mind. He listened and found out something about it. But most of these people don’t want to hear,’’ Williamson said.

The demonstrators included large numbers of civil rights movement veterans and college students from across the region who weren’t alive in the ’60s.

Elizabeth Redding, 63, of Willinboro, N.J. said she marched at Selma, Ala., when she was in her 20s.

‘‘This is worse, because we didn’t get the job done,’’ she said as she trudged up a hill leading to the park rally. ‘‘I never believed that this would be going on in 2007.’’

Tina Cheatham missed the civil rights marches at Selma, Montgomery and Little Rock, but she had no intention of missing another brush with history. The 24-year-old Georgia Southern University graduate drove all night to reach tiny Jena in central Louisiana.

‘‘It was a good chance to be part of something historic since I wasn’t around for the civil rights movement. This is kind of the 21st century version of it,’’ she said.

Red Cross officials manned first aid stations near the local courthouse and had water and snacks available. Portable toilets and flashing street signs to aid in traffic direction were in place. At the courthouse, troopers chatted amiably with each other and with demonstrators who began showing up well before dawn.

Sharpton said Bell, whom he spoke with Wednesday, was heartened by the show of support.

‘‘He doesn’t want anything done that would disparage his name — no violence, not even a negative word,’’ Sharpton said.

Reginne Gardner, 38, a black Jena resident, collected cash from protesters who parked their cars on the lawn of a relative’s home. Gardner said race relations in town have always been strained, but have grown even worse since this episode unfolded.

‘‘I hope this makes things better,’’ she said. ‘‘We all have to live here. I wish we all could get along, black and white.’’

Associated Press writers Michael Kunzelman in Jena and Errin Haines in Atlanta contributed to this story.