Mychal Bell, 17, one of the "Jena 6", is accused of beating Justin Barker in a school fight.
Earlier Thursday, Bell was moved from jail to a juvenile facility, according to his attorney, Lewis Scott.
LaSalle Parish District Attorney Reed Walters said his decision not to appeal was based on what he believed is best for the victim in the case.
He said a march by 15,000 people last week in the small town of 3,000 residents led by civil rights leaders Sharpton and Martin Luther King III did not influence his decision.
Demonstrators were protesting how authorities handled the cases of Bell and five other teens accused of beating fellow student Justin Barker.
Many said they are angry that the students are being treated more harshly than three white students who hung nooses from an oak tree on high school property.
The white students were suspended from school but did not face criminal charges. The protesters say they should have been charged with a hate crime.
Bell, now 17, was the only one of the Jena 6 behind bars. His bond previously was set at $90,000.
A district judge earlier this month tossed out Bell's conviction for conspiracy to commit second-degree battery, saying the matter should have been handled in juvenile court. The 3rd Circuit Court of Appeal in Lake Charles, Louisiana, did the same with Bell's battery conviction in mid-September.
Prosecutors originally charged all six black students accused of being involved in beating Barker with second-degree attempted murder and conspiracy. Walters reduced charges against at least four of them -- Bell, Robert Bailey Jr., Carwin Jones and Theo Shaw -- to battery and conspiracy.
Bryant Purvis awaits arraignment. Charges against Jesse Ray Beard, who was 14 at the time of the alleged crime, are unavailable because he's a juvenile.
Wednesday, Gov. Kathleen Blanco announced that Louisiana State Police officers will protect the families of the Jena 6 and investigate any threats they have received. A white supremacist Web site posted the names and addresses of the six black teens after last week's march, calling on followers to "let them know justice is coming."
Thursday, the FBI said it has been made aware of allegations of threats.
The December 4 attack on Barker came after months of racial tension, including at least two instances of fighting in the town, sparked originally when three white teens hung nooses from an oak tree on the town's high school grounds.
Walters has said there was no direct link between the hanging of the nooses and the schoolyard attack, and defended the prosecutions ahead of last Thursday's peaceful march. Blanco defended the prosecutor Wednesday, saying, "He has a solid record and is highly respected among his peers."
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