A group of influential art, historic preservation and free-speech advocates plans to put a measure on San Francisco’s March 2020 ballot that would preserve a controversial mural at George Washington High School that’s scheduled to be destroyed.

The San Francisco school board voted last month to paint over the 1,600-square-foot fresco, which depicts images of African slaves and American Indians that many, including students, find offensive and painful to look at. Ridding the school of the artwork, the board said, amounts to a form of reparations for the historic injustices against African Americans and American Indians.

“This mural is not teaching students about the history of slavery and indigenous genocide under George Washington or other white settlers,” said Nancy Truong, a 2013 graduate of the school who spoke at the meeting that decided the mural’s fate. “Instead it is teaching students to normalize violence and death of our black and indigenous community.”

But the mural has impassioned supporters, who pleaded with the board to preserve the piece as an important work of historical art, one that serves as an important reminder of the ugly events of the past.

Tension over the mural has simmered for decades.

The Depression-era mural entitled “Life of Washington” was painted by Russian emigre Victor Arnautoff, a student of the esteemed artist and muralist Diego Rivera. The scenes depicted in “Life of Washington” were intended to criticize the horrific subjugation endured by slaves and American Indians during the nation’s founding.

The pending ballot measure, championed by the Coalition to Protect Public Art, is still being written. But Jon Golinger, the group’s executive director and a veteran San Francisco campaign strategist, said the goal of the initiative is to ensure a greater degree of public input on decisions to destroy art freighted with historical significance.

“The bigger point is this: Who gets to decide something this drastic? The school board made a draconian decision to spend $600,000-plus to permanently destroy 13 murals of historical significance,” Golinger said. “We don’t believe that decision was made with ... enough decision makers.”

While school board members voted to destroy the murals, they conceded that the threat of a lawsuit and other hurdles may lead them to simply cover it up.

The coalition’s advisory board includes Matt Gonzalez, chief attorney in the San Francisco Public Defender’s Office, and Rocco Landesman, former chairman of the National Endowment for the Arts under President Barack Obama.

The proposed measure would likely contain two parts. The first would establish a policy declaration laying out how the city will handle proposals to destroy historic murals. The city’s Arts Commission has guidelines in place for those kinds of decisions on city property, but the commission’s authority doesn’t extend to buildings operated by the school district, Golinger said. The group’s ballot measure could change that.

The second piece of the measure would prevent the school board from destroying “Life of Washington” or other New Deal murals without first getting approval from the Arts Commission and the Board of Supervisors or from the voters. Golinger said he’s confident that, if passed by voters, the measure would be legally binding on the school board.

The group is open to options including covering up the offensive portions of the mural, so that students wouldn’t be forced to look at it, but could if they chose to.

“The goal is to get a compromise, so there’s a balance. We want to mitigate the impact on any student who feels pain from what they see in the murals,” he said.

A spokeswoman for the school district could not be immediately reached for comment.

Golinger said the group intends to submit the roughly 9,500 signatures the group needs to qualify for the March 2020 ballot by this November.

Dominic Fracassa is a San Francisco Chronicle staff writer. Email: dfracassa@sfchronicle.com Twitter: @dominicfracassa