By the time every member of Nansemond-Suffolk Academy’s class of 2015 had walked across the stage, a basket on the podium behind Head of School Deborah Russell had filled with dozens of marbles.

It was silly of her, Russell admitted, to think that she would escape the school year without a senior prank. Sure enough, most of the school’s 67 seniors surreptitiously placed a marble in Russell’s hand as they received their diplomas — although some, worrisomely, told her they had lost their marbles.

On a serious note, she used running metaphors to congratulate the seniors for finishing their first marathon — high school — and encourage them to finish college well.

“Don’t be content with the status quo,” she said. “Inspire others to finish the race.”

Russell said the class had been offered $2.2 million in scholarships and admission to 93 different colleges. She also noted accomplishments of the seniors in academics, sports and the arts.

Valedictorian Maya Venkataraman challenged her classmates to view the world — and others — as globes rather than maps.

Maps, she said, give the general idea but can distort reality.

“The world is nuanced, and maps are a simple definition of a complex concept,” she said. “Let’s enter and enhance the beautiful, round world.”

Salutatorian Matthew Allison said his one regret is that his introversion kept him from knowing his classmates as well as he could have, and he now was facing “losing contact with everyone just as I realized my mistake.”

But he looked on the positive side, seemingly confident he would see all of his classmates again.

“Many of us, it is said, will never see each other again,” he said. “I call that just plain negativity. We are one of the tightest-knit groups ever to come through here.”

The guest speaker for the morning was Congressman Scott Rigell, who challenged the graduates with a simple question: “Why not me?”

The negative answer to that question usually involves risk, Rigell said. He encouraged the graduates to be risk-takers, because risk “inevitably comes with anything worthwhile.”

“Challenges don’t pass any one generation,” Rigell said. “We’re going to need leaders to rise up in every area, so why not me?”