Tracy Miller, 27, is said to have sent multiple nude images of herself to pupils over the course of several months.
She was detained after one of the teenagers went to superiors at the school and showed them one of the explicit images.
School bosses were already conducting an investigation after rumours began to go around about the allegations at Logan High School, West Virginia.
Miller had been employed at the school since January working as a health instructor but has since been suspended.
Logan County Sheriff deputies have now taken over the investigation – arresting on suspicion of three counts of distribution of obscene matter to minors.
Police are appealing for any other students who may have been sent indecent images to come forward.
Logan County School released a statement saying: “We are dealing with the situation by following county policy governing Employee Code of Conduct.
“The teacher in question has been suspended at this time.”
Logan police’s Sgt Nick Booth urged mums and dads to “monitor what is going on with the phones and pads on any social media platform”.
Miller has been released on bond while the police continue to investigate.