PLAINFIELD (CBS) — The athletic director at Plainfield North High School has resigned, after an investigation into an alleged affair with a former student, sources said.

Doug Stevens was put on administrative leave for about a week before the board accepted his resignation. Police were not involved in the investigation, and district administrators looked into the issue themselves, sources said.

The investigation showed that Stevens did not have a relationship with the student until after she graduated from Plainfield North High School in June, 2010. However, district administrators did encourage Stevens to resign, sources said.

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Stevens’ wife, Jovy Stevens, has petitioned for a divorce. She cites irreconcilable differences as the reason for divorce and also accuses him of “extreme and repeated mental cruelty” and also accuses that he’s guilty of adultery. Doug Stevens agreed about the irreconcilable differences, but strenuously denied the other allegations.

This is the second incident this year where staff has been accused of having inappropriate sexual relationships with a student at Plainfield North High School.

Plainfield North teacher Ashley M. Blumenshine , 27, of Lisle is charged with aggravated criminal sexual abuse. She was allegedly found with a 16-year-old student in a car behind a department store on Route 59 on Jan. 4. Blumenshine pleaded not guilty to the charges in January.

Blumenshine was a P.E. and dance teacher since 2006 in the Plainfield School District. Blumenshine resigned from her tenured position at Plainfield North after her arrest.

A Plainfield North parent, who didn’t want her name used, said students were upset another incident between student and staff was happening at their school.

“The girls were saying how uncomfortable they are feeling with all that has been happening,” she said. “These kids should not have to be thinking of such possibilities, school is hard enough and now they have to worry if staff members are checking them out. As a parent this makes me worry when I see my child leave for school. I am so sad for our students they do not need this nor deserve such pain, they should be able to go to school and not only learn but trust their teachers without any hesitation.”

Stevens was hired as athletic director at Plainfield North on Aug. 27, 2009 after serving one year as the athletic director at Peotone High School.

(Source: Sun-Times Media Wire © Chicago Sun-Times 2010. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)