The Prince George's County Board of Education voted last night to make the Rev. Dr. Martin Luther King Jr.'s birthday and Rosh Hashanah official school holidays after years of controversy on the matter.

The board unanimously approved School Superintendent Edward J. Feeney's school calendar, which for the first time includes Jan. 15, King's birthday, as a holiday. By its vote last night, Prince George's joins the District of Columbia, and Montgomery and Fairfax counties in observing the slain civil rights leader's birthday by closing schools.

Fairfax County joined the other jurisdictions just last year be declaring the third Monday in January as Lee-Jackson-King day, which honors King and Confederate Civil War heroes Robert E. Lee and Stonewall Jackson.

Arlington and Alexandria are now the only jurisdictions in Metropolitan Washington that have not made King's birthday an official holiday. The Prince George's board also voted to make Sept. 11, Rosh Hashanah, the Jewish New Year, a school holiday.

In other action, the board gave final approval to a plan to reduce busing in the county's elementary schools. The plan is designed to shorten or eliminate the bus rides of 3,619 students starting next fall. Approximately 1,440 of those students would be able to walk to school.

The county NAACP branch has said that it would take the school board to court if the plan were approved.