Lynne Mooney Teta on Tuesday announced her resignation as headmaster of Boston Latin School, the prestigious exam school that has spent the past six months under a magnifying glass over racial issues.

In a letter to the BLS community, Mooney Teta, herself a BLS graduate, wrote, "I believe that it is time for a new head master to lead the school and carry on the tradition of excellence.

"While I am saddened to leave Boston Latin School -- the school from which I graduated in 1986 and which first inspired me to become an educator -- I believe that our mission remains steadfast. Boston Latin School has and will continue to provide an unparalleled contemporary classical education to our students so that they may pursue successful college studies, become responsible and engaged citizens, and enjoy a rewarding life.

"We have faced challenges this year, and I have been greatly encouraged by the commitment of students, faculty, families and alumni to work together to collaboratively address issues of racism and discrimination in our community."

An otherwise normal school year changed on Martin Luther King Day, when two black seniors posted a YouTube video about the discrimination they and other black students said they had encountered in their time at the school.

The NAACP ultimately called for Mooney Teta's resignation and the US Attorney's office started an investigation into possible civil-rights violations.

School Superintendent Tommy Chang accepted her resignation.

In a memo to the School Committee, he praised her achievements - BLS sent more students to Harvard than any other high school in the world this year and said she worked hard to address the racial issues raised by black students:

"Under Lynne's guidance, BLS faculty worked with student leaders to develop a comprehensive plan to create a more welcoming and inviting environment for all students. These efforts must continue, but I feel confident that the steps taken have firmly put BLS on a path of continued growth."

He added: "As we look to conduct a national search for the next Boston Latin head master, I want to urge the BLS community to come together and support the transitional leadership team. Boston Latin School represents an educational experience that is unrivaled among public and private schools, and we are committed to ensuring that its tradition of excellence continues to thrive."