(CBS) – A Plainfield Central High School science teacher is accused of sexual misconduct with a 17-year-old student.

On Friday, bond was set at $600,000 for the teacher, Brian D. Smith, a 32-year-old married father of three.

Will County Assistant State’s Attorney Mary Fillipitch says Smith contacted the student online, called himself “Andy” and asked if she “thought Mr. Smith was sexy.” He allegedly wrote that he knew how she could do better in his class.

Prosecutors said that for a month Smith and the girl texted and sexted each other. Two weeks ago, after he changed her grades on several assignments and a test, they allegedly engaged in sexual contact in a supply closet.

The girl told authorities she feared Smith would flunk her if she refused his advances.

Fillipitch had urged the judge to set bond at $1 million. Smith is charged with one count of criminal sexual assault.

Smith had taught at the school for the past three semesters. Administrators removed him from class Monday, have barred him from the school and have prohibited him from contacting staff or students.

Brian D. Smith (Will County State's Attorney)

Brian D. Smith (Will County State’s Attorney)