Libertyville High School band director Jeffrey T. Daeschler has been on paid administrative leave since November, District 128 officials have confirmed.
But district officials won't say why, citing legal privacy concerns.
"It is a personnel matter which we are not able to discuss," Libertyville-Vernon Hills Area High School District 128 spokeswoman Mary Todoric said.
Superintendent Prentiss Lea also declined to elaborate on the matter.
Daeschler did not respond to an emailed interview request.
Daeschler has led the school's bands since 2010. He previously had served as band director at Stagg High School in Palos Hills and at downstate Rantoul Township High School.
He also taught at the University of Illinois at Urbana-Champaign and conducted the university band.
Daeschler's classes at Libertyville have been picked up by other staffers and part-time teachers, Todoric said.
Daeschler's biography remains on the music department's website.