Officials at Greenfield Central High School say the poster is not what it might seem at first glance, but is promoting a play about the evils of racism, WISH-TV, Indianapolis, reported Tuesday.
Greenfield Principal Steve Bryant said seeing the poster out of context can be misleading.
"If you move beyond that banner, there were several other banners that depicted (Martin Luther King Jr.'s) movement in the '60s," Bryant said.
The poster is promoting the school play "To Kill a Mockingbird," based on the 1960 Harper Lee Pulitzer Prize-winning book about racism, he said.
Some parents, however, say they're unhappy about the poster.
"It must come down," said a woman who posted a picture of the poster of Facebook, saying it's the first thing people see when walking into the school.
Bryant notes that "To Kill A Mockingbird" is on the eighth-grade reading list, and pictures of the KKK are in approved Indiana textbooks.
"I guess, what I would say to that parent or parents, is, 'Please come in and dialogue with us. Talk to us. Have a meeting with us. Come in and see the play,'" Bryant said.