The parents have filed a lawsuit against the teacher, John Freshwater, and the Mount Vernon school district, The Columbus Dispatch reports. They claim that Freshwater also told his students that intelligent design was true.
"Mr. Freshwater advised his students that although he is forced to teach from the textbooks, the teachings are wrong or not proven according to the Bible," the suit states.
The parents say that Freshwater used a piece of electrical equipment to etch a cross on their son in December. When they complained, the district responded by telling the teacher not to do anything similar in the future.
Administrators began cracking down on the teacher only after the parents hired a lawyer, the suit says.
The district says it has launched its own investigation and expects to release a report on Friday.
In April, after Freshwater agreed to remove most religious items from his classroom but refused to move a Bible off his desk, students rallied to support him.