It is reported that rumours of the abuse went around the school in December with the student eventually telling police what happened with the two women.
The other woman who was allegedly involved with the threesome has not been charged as she has since left the school.
While the age of consent in Oklahoma is 16, adults can still be charged for sexual assault if they were in a position of authority over their victim.
In this case Churchwell was the boy's volleyball coach. She has since been on a leave of absence from her job.
A social media account that appears to belong to the teacher makes references to her Bible studies and volleyball coaching.
Berryhill High School is co-operating fully with the investigation into Churchwell's alleged crimes.
"Berryhill School District takes the safety of its students very seriously and does everything it can to provide a safe learning environment," said a spokesman.