sidney_a._ribeau.jpgWASHINGTON (AP) – Howard University's president says he's stepping down at the end of the year after five years heading the private, historically black university. Sidney A. Ribeau announced Tuesday he would retire at the end of December.

A letter signed by Ribeau was posted on the school's website, and a second letter from the chair of the school's Board of Trustees announced that Wayne A.I. Frederick will become interim president.

The school enrolls around 10,000 students.

Ribeau was named the 16th president of the school in 2008. Before that, he spent 13 years at the head of Bowling Green State University in Ohio.

Howard has been facing financial challenges.

Earlier this year Moody's Investors Service downgraded the school's credit rating, citing revenue declines and automatic federal budget cuts from Congress.