In the minutes before the 300-plus graduates of the New Canaan High School Class of 2015 marched up to get their diplomas, Stephen Vehslage told them the wider world they are entering can seem like a turbulent place because of changes across technology, culture and global affairs.

“Understand during your formative years the world as we know it was fundamentally reshaped,” Vehslage said. “A lot has changed to put it mildly and there is more to come.”

Vehslage was the commencement speaker at New Canaan High School’s 2015 graduation ceremony Thursday night at Dunning Field.

Vehslage, who became a history teacher at the school in 2001 as the graduating class walked into school in a country where ubiquitous social media, the Sept. 11 terrorist attacks and “seemingly perpetual” War on Terror, government surveillance, Facebook and the Great Recession transformed the landscape.

Social media and the Internet are a profound, “tectonic shift,” that has brought both good and bad, Vehslage said.

“We have a whole new vocabulary now. The whole American lexicon has changed...,” Vehslage said. “You have lived through a paradigm shift and it is your generation, not mine, that will determine how it will play out.”

But the good news is that the fundamental virtues, advice and precepts for living a happy and fulfilled life remain the same, Vehslage said.

“Human nature hasn’t changed, and what it means to be a good person who carries themselves with dignity, integrity and kindness hasn’t changed, “ he said. “... Life is complicated and sometimes turbulent but the big stuff that really anchors us is actually pretty simple.”

During his remarks, Vehslage also noted encouraging signs such as U.S. economic indicators showing steady growth since 2009, booming stock markets, and more broadly across the world poverty receding and educational levels rising, and child mortality and AIDS transmission rates dropping quickly.

“Since you’ve walked into pre-school dwarfed by your backpacks the national debt has jumped from 6 to 18 billion dollars and we’ve lived through the worst economic crisis since the Great Depression,” Vehslage said. “... But the truth is that on balance the world is a wealthier, healthier, and safer place to live.”

Vehslage concluded by recounting how he gave up a career as a successful attorney in the late 1990s to go back to school to become a teacher, a career transition that created strain and self-doubt and tested his resilience.

Vehslage read a quote by George Bernard Shaw sent to him by his sister-in-law he said he hoped would inspire the students to commit themselves to larger principles.

“Be used as a purpose recognized by yourself as a mighty one,” Vehslage read. “... I am of the opinion my life belongs to the whole community and as long as I live it is my privilege to do for it as much as I can.”

During the ceremony four seniors — Corinne Vietorisz, Matthew DeMattia, Shaun Appel, and Sean Davidson — were chosen by school administrators to speak during the Moments of Reflection on their high school experience.

Vietorisz told the audience she had long looked forward to graduation as the start of adult life but is now wistful about the closing of a chapter where there has been a general atmosphere of curiosity, good will, tolerance and selflessness among her classmates.

“Despite my new adult status I haven’t mastered the adult things but maybe the adult things aren’t the most important all the time,” Vietorisz said.

The Class of 2015 included sports teams that spent hours practicing “just to get better,” and more advanced students who have given their time to tutor classmates in complex subjects.

Whether playing in school or after-school bands, producing videos, or playing sports, students have grown more accomplished by being encouraged and allowed to do exactly what comes naturally, Vietorisz said.

She hopes that doesn’t change now, she said.

“I have a physics genius friend who put her studying on hold just to have a study session for us because she wanted to share a subject she loved,” Vietorisz said. “When you take a step back and look, we’ve done a pretty good job for a bunch of kids. We may be adults now, but we’re not ready to grow up quite yet.”

Veronica LeDuc, who was hired as assistant principal in 2011 and became acting principal this year, confessed the Class of 2015 has a special place in her heart because she became an administrator at the school when they were freshmen.

LeDuc said in particular the students in the class were mature beyond their years, particularly in how they embraced a wide diversity of opinions and attitudes within their group.

“You are an eclectic group of individuals and at a time in your life where it is common to want everything to be homogenized and not want anything to stand out, you have learned to celebrate your differences,” LeDuc said.