Defenders of this law often claim it's only meant to teach critical thinking and provide academic freedom to teachers who want to challenge evolution scientifically. There is no scientific controversy over evolution or climate science for these teachers to discuss, though. The only reason to have this law is to sneak non-science, like creationism, into classrooms.
The purpose of the law becomes even more clear if you listen to its legislative sponsor. Louisiana state Senator Ben Nevers said (pdf) that the Louisiana Family Forum, a powerful lobbying group for religious rights, suggested the law to him:
"[The Family Forum] believe that scientific data related to creationism should be discussed when dealing with Darwin's theory."
These anti-science laws are not just a Louisiana problem; they're an American problem.
In 2012, Tennessee passed its own creationism law, based off the model in Louisiana. Each year, dozens of states around the country have creationism bills introduced. This year, bills have already been killed in states including Oklahoma, Colorado, Montana, and Arizona. We still have a creationism bill in Missouri to defeat this year. Next year, a whole new set of creationism bills will be introduced.