A packed crowd of parents and siblings attended Loudoun Valley High School's commencement Friday, looking down from the school's football stands at the 360 graduating seniors in their green and white gowns.

Guests also included an array of uniformed Loudoun County sheriff's deputies and security guards, posted in all directions and scanning the crowd from behind dark sunglasses.

Security was tight because of the day's commencement speaker, John E. McLaughlin, deputy director of the CIA. School officials said weeks ago that the CIA's number-two man would speak at the event. In the intervening time, however, CIA Director George J. Tenet announced he was resigning from the agency in mid-July, leaving McLaughlin as its interim head.

The news led to some anxious moments at the Purcellville high school. Would McLaughlin be too busy to visit? When asked Wednesday whether the speech was still on, Valley Principal Gerald G. Black laughed. "As far as we know," he said.

McLaughlin made it, all right, entering the stadium shortly before the graduates streamed in and taking a seat on a podium in the middle of the football field. He sat beside Black and School Board member Priscilla B. Godfrey (Blue Ridge), whose son graduated with the class.

McLaughlin promised the crowd he would be brief. "My profession is one of very few words," he joked.

He told the graduates they would be surprised by the course their lives would take. He recalled flying over a mountain pass in Central Asia in a decrepit Russian-built helicopter. The chopper, with fuel tanks built inside the cabin, smelled heavily of gas. McLaughlin looked up at the pilots and noticed both were smoking.

"At times like that, I ask myself, 'How did a nice boy from western Pennsylvania end up here?' " he said.

"Always be open to the possibilities that life puts before you," McLaughlin told the audience. "You may find, as I have, that they are greater than your plans, greater than your hopes, even perhaps greater than your dreams."

McLaughlin alluded to some of the recent controversies surrounding the accuracy of U.S. intelligence, telling the graduates that despite criticism and pressure, he has been proud of his three decades at the CIA.

"I wish I could say we were perfect, but we're not," he said. "Life is too complicated and too unpredictable to expect perfection. And intelligence officers have to deal with some of the most complicated and least predictable things on the planet."

McLaughlin also told the students that Sept. 11, 2001, was a moment that carried with it a "profound sense of challenge and change" for them.

He told the graduates that their leaders have been forced to confront the new world by making decisions girded by personal values, and he challenged them to do the same in their own lives.

Shortly after delivering his speech, McLaughlin departed, offering graduates a snapped salute as he walked toward a waiting van. His security left with him, and the Loudoun deputies who remained relaxed noticeably, as one pulled out a water bottle and another put down binoculars he had been using to watch the crowd.

CIA spokesman Tom G. Crispell said this was the only high school graduation speech McLaughlin delivered this year. He said McLaughlin, a Loudoun resident, was invited by the school's senior class president and accepted because he thinks it is important to tell young people about the value of public service. Crispell noted that his boss speaks publicly before other groups with some frequency, including the Council on Foreign Relations.

Although some graduates said they were distracted during the speech -- anticipating their walk across the stage to receive their diplomas -- others said they were inspired.

"It seemed like he put a bit of time into putting the speech together," said graduate Nathan Gurevitz, 17. "It was nice he was here. Obviously, he's a very busy man."

John E. McLaughlin