MORAGA — Saint Mary's College has punished a singing instructor, who is the brother of a college trustee, for his choice to use a song that uses racist terms in a voice class last month.

College leaders said Monday the incident called into question Louis Lebherz's future at the school. The musician already has been forced to apologize to the class and to complete diversity training, said Beth Dobkin, the college's provost.

Lebherz, an artist in residence at Saint Mary's, had been asked to teach classes this year, Dobkin said. His choice to use the original version of the show tune "Old Man River," which refers to slaves and African-Americans in derogatory terms, will affect his employment, she said.

"It already has, but I can't tell you to what extent," Dobkin said. "We're continuing to discuss our future relationship with him."

Lebherz did not respond to messages left on his home and mobile phones Monday. His brother, Saint Mary's trustee Philip Lebherz, also did not respond to a phone message.

In a letter written to the African-American student who raised the complaint, Lebherz apologized for his choice of the original score. The offensive language was taken out of later versions of the song.

"I sincerely wish to apologize to you for my insensitivity in having a student sing a song which called attention to the racial problems that were and are a serious problem for our nation, and also for our own institution," Lebherz wrote to senior E.J. Youngblood.

The incident came at a particularly fragile time for the Catholic school. Administrators have tried to make the college a more welcoming place for minorities since 2008, when regional accreditors criticized the school for having shoddy race relations and a lack of diversity.

Accreditors earlier this year commended the college for improvements, but students this month protested several areas of weakness, including a lack of tolerance among employees and a shortage of minority professors. Youngblood said he does not think the college has responded strongly enough to his grievance.

"I want him to be fired but, realistically, I know that's not going to happen because his brother is on the board of trustees," said Youngblood, who dropped Lebherz's class after the March 4 incident.

Dobkin said the college has followed its disciplinary rules to the letter and that she does not know of any contact related to the matter between Philip Lebherz and college officials.

Matt Krupnick covers higher education. Contact him at 925-943-8246. Follow him at Twitter.com/mattkrupnick.