William Reames, 30, of Cleveland, pleaded guilty to four counts of rape last month. Police said Reames and the girl had a consensual yearlong relationship.
Reames apologized in court.
"I feel terrible about what's happened," he said. "I know that down the road she may have some problems, and I'm genuinely concerned about that, and I pray for her every day."
An attorney spoke on behalf of the girl's family.
"For the sake of all parents and their young children, we ask your honor that William Reames receive, the harshest punishment so he can never again destroy the life of an innocent child," said Patrick DeAngelo, the victim's attorney.
Cuyahoga County Common Pleas Judge Nancy McDonnell could have given Reames up to 40 years in prison.
Reames had been a teacher at Laurel School for three years. The school fired him after he pleaded guilty.