The Grant High School District 124 board accepted the resignation Wednesday morning of a female science teacher who allegedly had inappropriate contact with a student.
Superintendent Christie Sefcik acknowledged the resignation, but refused additional comment.
The Daily Herald is withholding the name of the eighth-year teacher pending criminal charges.
Sefcik would not say whether the teen involved in the relationship was a student at Grant High School in Fox Lake.
Sefcik said in a letter sent home to parents that administrators received information alleging the inappropriate contact on Oct. 6, and that Grayslake police were contacted to investigate the matter.
Sefcik said this is an "isolated incident that occurred away from campus and involved no other students."
Grayslake Police officials said the allegations are under investigation and it is unclear at this point whether charges will be filed.
The teacher filed a resignation letter after the investigation started, Sefcik said, but by law, the district had to accept the resignation during the special board meeting.
"While I understand you may have additional questions, this is a police matter now and we must allow them time to conduct a thorough investigation," Sefcik said in a statement to parents Tuesday. "During the course of the investigation, any information regarding this matter will come directly from the police authorities."
Grayslake Police Chief Phillip Perlini said his department is working with District 124 staff and the Lake County state's attorney's office in conducting a thorough investigation. He said the victim is a juvenile and no further information will be released until the investigation is complete.