A former Clearwater High School instructor was sentenced Tuesday to two years in prison after authorities said he had an ongoing sexual relationship with a student.James Millard Knuckles, 45, of New Port Richey pleaded guilty to one count of unlawful sexual activity with a minor. His prison sentence will be followed by three years of sexual offender probation with no option of early termination, as well as a lifetime sex offender designation.Police say Knuckles met the girl through the school's Junior Reserve Officer Training Corps program, where he was one of two instructors. District spokeswoman Lisa Wolf said Knuckles was terminated Feb. 16, three days after his arrest.Investigators say he and the girl had sexual contact over "an extended period of time" at various locations throughout the county but not on school property. Detectives started investigating after learning of a relationship from student rumors.Contact Colleen Wright at [email protected] or (727) 893-8643. Follow @Colleen_Wright.