Paint brush in hand, President Bush helped spruce up a high school Monday and tried to draw attention to a broader point — the value of community service on a day honoring the Rev. Martin Luther King Jr.

"I encourage people all around the country to seize any opportunity they can to help somebody in need," Bush said from the library of Cardozo High, a predominantly poor, minority high school about 10 minutes from the White House.

"By helping somebody in need, you're honoring the legacy of Martin Luther King," the president said. "And by helping somebody in need, you're really helping yourself; you're lifting your soul."

Monday was a federal holiday for King, the slain civil rights leader who built a life around racial equality, nonviolent protest and public service.

Bush said people should treat the day as King's late wife, Coretta Scott King, wanted it. "It is not a day off," Bush said. "It's a day on."

In an unannounced visit, the president joined a community clean up project at Cardozo, where classes were not in session. A few hundred children, parents and local volunteers were at the school, many of them painting murals in the hallways to give the place a livelier look.

Bush, in rolled-up shirt sleeves, walked along a corridor and chatted up the volunteers, including Attorney General Alberto Gonzales.

Bush borrowed a paint brush dabbed in red ink, then carefully colored in the "B" of a stenciled drawing of "Ben's Chili Bowl." The local eatery is a Washington institution, known for its famous chili dogs and its rich history, including surviving the riots after King's assassination.

"Getting the drift of this thing here?" a smiling Bush asked as he painted, seeking approval of his technique. Volunteers nodded yes.

Upstairs in the school's library, children wrote hopeful letters to people in New Orleans who lives were devastated by Hurricane Katrina. The kids seemed unfazed by the presidential visit until Bush entered, and many jumped on chairs to get a glimpse of him as he thanked them.