Johnthony Walker, 25, is facing statutory rape charges after he allegedly confessed to having sex five times with a 14-year-old.
Police in Tennessee say Walker was staying with the child's family for the last few months.
Walker was sentenced to four years in prison after the deadly crash, but was released on bond while his appeal is pending.
His bond was set at $350,000.
Official: 6 dead in Chattanooga elementary school bus crash
At least 6 children killed in Tennessee bus crash