The San Francisco Board of Education voted unanimously this week to cover a series of murals at George Washington High School that includes images of a dead Native American and slaves at work.

A debate about the series of 13 murals, called “The Life of George Washington,” has been going on for over half a century, but has heated up in the past couple of years. The seven-member board’s decision came Tuesday, during the panel’s last meeting of the school year.

“I didn’t know how the board would vote, but it was important that we not put this off any longer,” Stevon Cook, the board’s president, said in an interview Thursday night.

Those in favor of covering the murals have said some of the images are offensive to various groups. Some in favor of keeping them see artistic value in the work, which was created in the 1930s for the Works Progress Administration by Victor Arnautoff, a Russian-born artist, social realist and Communist who was critical of the country’s first president.