NIKI KAPSAMBELIS
Mr. Stehlik’s Opus
Reflections on a 40 Year Teaching Life
As Mark Stehlik moves toward his next chapter, former students recall the pivotal role he played in their own stories
Like any good tech origin story, the tale of Mark Stehlik’s extraordinary legacy begins in a garage.
When he was in second grade, a family from Costa Rica moved next door to his family’s row house in Queens, New York. Young Mark became fast friends with their son, Carlos, who needed to speak English with a peer.
Armed with a blackboard easel that his mother put in the garage, Stehlik helped his new friend learn, and the two boys spent hours talking, playing and developing a lifelong friendship.
“I just liked teaching, and I liked the fact that I seemed to be helping him,” Stehlik recalled.
It was a welcome oasis from the trials of elementary school, where, as he now puts it, “Nobody likes the smart kid — especially the smart kid who doesn’t really have a lot of other things to bring to the table.” The same year Stehlik was teaching his friend to speak English, his teacher was banishing him to a closet for disrupting the classroom.
But in fifth grade, a teacher recognized that he was gifted in math and assigned him problems that weren’t part of the curriculum. It was a profound experience.
“What it told me is: You need to figure out where people are coming from in order to get them further,” he said recently.
Camille Fournier (SCS 2001), former Chief Technical Officer at Rent the Runway
If you Google the name “Mark Stehlik,” you won’t find a Wikipedia page, although many of his former students have them.
What you will find is the low-tech personal page he maintains as the Assistant Dean for Outreach and Director of the Undergraduate Computer Science Program.
It’s a snapshot of his mind, full of notes, links and observations that are important to him, including quotes from sources as varied as former students, Socrates and Indiana Jones.
His advisee alumni — who total roughly 4,000, and he has taught countless more — have gone on to become some of the most important voices in their fields. You might not realize it, but Mark Stehlik’s influence is, in some sense, all around you: in the iPhone you’re holding in your hand, in the computer science class your child is taking, in the map of the human genome that may one day save your life.
Students have named their kids after Stehlik, and in one case, their company. He officiated at one wedding and served as best man at others. The depth of his impact is impossible to measure; as technology executive and author Camille Fournier (SCS 2001) put it, “If Mark Stehlik needed a kidney, the line to donate would be around the block.”
Another, when named to TIME magazine’s list of the world’s 100 most influential people, told Stehlik: “This would not have been possible without you.”
Stehlik’s office has provided sanctuary to thousands of undergraduates: a place to vent, pull pranks, laugh, celebrate or melt down. It is the physical embodiment of Mark’s home page, filled from floor to ceiling and wall to wall with artifacts of a teaching life. Because at his core, regardless of what title happens to follow his name, Mark Stehlik is a teacher.
In one of the most celebrated computer science schools in the world, one of the most beloved figures is a man who collects fountain pens and books. His first fountain pen, he points out, was filled with green ink — not red. It’s a metaphor for how Mark Stehlik approaches his craft: finding ways to say go when everyone else is saying stop.
Owen Astrachan, Professor of Computer Science at Duke University
In the summer of 1983, Owen Astrachan, a high school teacher from North Carolina, arrived on campus to take a workshop designed to train the first teachers of AP Computer Science. The first advanced placement (AP) computer science exam was then a year away.
His teacher was Mark Stehlik, who by now was a year into his official designation as “special faculty” — now known as teaching faculty. So inspiring was the experience that Astrachan decided to return to graduate school and teach at the university level.
He and Stehlik both became readers for the national AP exams, which in those days were taken on paper. High school and college instructors convened at one location to grade the exams; eventually, Astrachan became the chief reader, overseeing the grading of the exam for the entire nation’s high school students — a role that Stehlik would later take over.
Today, Astrachan is a professor at Duke University, where he leads the undergraduate computer science program and enjoys considerable status in his own right. When Carnegie Mellon named Stehlik a University Professor in 2023 — becoming the only teaching-track faculty member to earn the university’s highest honor — Astrachan wrote a letter of support.
“Humanity just kind of oozes out of Mark,” Astrachan said. “He was always giving, nurturing and trying to get you to be the best version of yourself, without telling you that’s what he was doing.”
Dawn McCullough, Lead Computer Science Teacher at South Fayette High School
Dawn McCullough, who was just starting to teach high-school computer science in 2017, recalls Stehlik substitute teaching at her school in suburban Pittsburgh to cover for an ill teacher.
“He would come here every day and teach the course for 50 minutes and go back to work,” she said.
The 11th and 12th graders in the class could not stop talking about him.
“Love probably isn’t a strong enough word,” McCullough said. “They admired him; he inspired them. He created an environment where the kids couldn’t wait to come to class.”
Melissa Goldman, Partner at Goldman Sachs
In 1988, six years after Stehlik volunteered to teach his first CMU course, he became an advisor.
What he didn’t know at the time, but came to understand much later, was that advising was teaching; the only difference was that instead of explaining for-loop statements, he was explaining life.
“It’s this process where you’re trying to take someone from where they are to where they need to be in order to pass the course,” Stehlik explained. “Some of those people go willingly, and some of those people will struggle. Trying to figure out how to support them is the job of a good teacher.”
Melissa Goldman, who graduated with the first cohort in 1992, credits Stehlik with shaping her career path. Now a partner at Goldman Sachs, she met him the summer before her senior year in high school, when he taught a pre-college program she attended.
“He made programming interesting, and fun, and approachable,” she said. “It was really through my summer of learning with him in that role that made me confident and excited about the idea of what being a part of that discipline would enable me to do. It was creative; it was analytical; it was precise; it was artistic. It was all those things rolled into one.
“His advocacy for his people, his students, goes way beyond the university setting,” said Goldman, who has worked with colleagues whose children are now advised by Stehlik.
When people ask her about her own job experiences, she answers: “It all comes back to Mark.”
Josh de Cesare (ENG 1996, SCS 1996), part of Apple’s original iPhone team
It took Josh de Cesare (ENG 1996, SCS 1996) some time to warm up to Stehlik.
A transfer student from California, he arrived in Pittsburgh in the early 1990s on his first-ever airplane trip, broke and without a place to live. He met with Stehlik, his new advisor, to figure out his course schedule and transfer credits.
“I remember him almost brushing me the wrong way: why is this guy telling me this class doesn’t count?” de Cesare recalled.
After realizing that Stehlik was trying to help him, de Cesare dove into his education. A self-described “aggressive student,” he was determined to learn everything he could.
“I took way too many classes, and he helped push back — just a little bit — to make sure that I would fail gracefully,” de Cesare said.
Once, de Cesare jokingly badgered Stehlik to move a required class so he could take an elective that seemed interesting. Eventually, they agreed to settle the matter with a game of ping-pong in the student lounge.
“Everyone found out this was happening, so the room was packed, which didn’t help. I put up a good fight, but I think Mark got me by 3 or 4 points,” de Cesare said.
His revenge would come later, when de Cesare and some friends rigged a cardboard box loaded with a few thousand ping-pong balls to the top of Stehlik’s office door. De Cesare and his friends waited inside the office with a video camera, capturing the moment when Stehlik shoved open the door and was showered with the white plastic balls.
Now employed by Apple, de Cesare was part of the original iPhone team and prepared the prototypes that Steve Jobs demonstrated to Apple’s board of directors. De Cesare gave the prototypes to Apple’s archival group. On his desk, he displays a more personally meaningful memento: a ping-pong ball that Stehlik gave him, along with his diploma, at his graduation ceremony in 1996. On it is printed “congratulations + thanks.”
“His story isn’t in what he says he is or what he says he does. His story is in the lives that he’s touched.”
— Marcin Krieger (SCS 2000)
Marcin Krieger (SCS 2000), Attorney at ReedSmith
If you want to rile Mark Stehlik, suggest to him that he should give every student he advises the same breaks. He’s a qualitative guy in a quantitative environment.
“Everybody has different personal circumstances; some of those that weigh on them. Some of those that suddenly occur. Catastrophes at home, catastrophes here. I would have taken a lot more psychology courses as an undergrad if I knew what I was going to be doing with my life,” he said.
If you feel broken, and you go to Stehlik’s office, he is going to find ways to get you through the semester.
“That’s what they pay me to think about,” he said. “My job isn’t hard. Most of what my job entails is caring and not being judgmental.”
Marcin Krieger (SCS 2000), now an attorney, remembers his four years as an undergraduate as the most challenging of his life. His own parents had moved to Europe the same year he started college. For four years, he was alone. He spent Thanksgiving at Stehlik’s house, as did many students.
As Krieger struggled with his grades, Stehlik asked him if he had considered transferring to a different department. Krieger, a high achiever, responded by adding more work, tacking on first a second major, then a minor.
Sometimes, the stresses of his life weighed so heavily on Krieger that he would just take cookies into Stehlik’s office and sit on the floor, eating, while his advisor worked. “When I was ready to talk about what was bothering me, he’d listen.”
Now friends as adults, the two men often meet for dinner. Krieger marvels at the fact that when they met, Stehlik was the age that Krieger is now. He imagines some depressed kid sitting on the floor of his own office, eating cookies, knowing it would seem weird: “But Mark just rolled with it.”
“His story isn’t in what he says he is or what he says he does. His story is in the lives that he’s touched,” Krieger said. “I’m so lucky that he is a part of my life now. I wouldn’t be here today if he wasn’t a part of my life then.”
Michael Schatz (SCS 2000), Professor of Computational Biology and Oncology at Johns Hopkins University
Michael Schatz (SCS 2000) arrived on campus in 1996. His first year was a wonderland: coming from a small town in upstate New York, he was largely self-taught in computer science.
“CMU was just incredible,” he recalled. “So creative and energetic.” Everywhere he went, there were smart people.
He met Stehlik while taking a course as a freshman. The two built an immediate trust, and Stehlik became his advisor.
But in the second year, Schatz struggled. He felt out of his element, like he was hitting a wall. His self-confidence crumbled, and he was on a downward spiral. Like Krieger, he recalls that moment as the worst in his life.
Stehlik was his lifeline.
“Mark believed in me,” says Schatz. “He really believed in me.”
Together, they plotted Schatz’s life plan: what was really important? What really mattered? Stehlik told him to throw away his expectations and helped him understand that everyone goes through their journey at a slightly different rate.
Not only did Schatz get back on his feet, he soared. His grades rebounded and he was eventually able to rediscover himself. He graduated and went on to earn his Ph.D. Today, he runs a genomics lab at Johns Hopkins that uses machine learning to create medical and genetics breakthroughs. In 2022, Schatz was recognized as one of TIME magazine’s 100 most influential people in the world.
Shortly after the TIME ceremony, Schatz visited CMU. His first stop on campus was to thank Mark in person for everything that he had done. “It’s a direct path from Mark to that recognition, which I cherish,” he said.
Nathaniel Manista (MCS 2002, SCS 2002) pictured with Stehlik
Nathaniel Manista (MCS 2002, SCS 2002) added computer science as a second major during the autumn of his senior year. After meeting with Stehlik, Manista decided to complete the entire degree in roughly three semesters — a punishing workload by any measure.
A few months later, in the summer of 2001, Manista’s mother died. The next semester, he faced a heavy load of coursework and other personal problems. Manista took an incomplete and faced a spring with two more difficult courses that, despite their rigor, did not offer him enough credits to earn his dual degree; he was short by 3 units.
Stehlik offered him a way out: he could take a 3-unit independent study course, which would involve learning the game of darts by playing in the basement of Stehlik’s home every Sunday. Manista agreed.
“We’d throw darts, talk character, politics, current events — all kinds of different things. Gossip,” said Manista. His final was the sum of five darts on the board; the first dart he threw was a triple 20, which guaranteed a pass.
They continued throwing darts for years, well past graduation. In later years, Manista’s future wife, Krista, accompanied him. When they married, Stehlik served as best man; he toasted the young couple, his daughter caught the bride’s bouquet and Stehlik drove the bridal car back to their hotel. Each year, he texts them on their anniversary.
“He was not just parenting this enormous community of CS students, but he was also an incredible father and spouse, and now an incredible grandfather,” said Krista Stone-Manista, who saw Stehlik and his wife, Sylvia, as role models for her own marriage. “He seems to be having so much fun.”
From left to right: Sabih Bin Wasi (CMU 2015), Rukhsar Neyaz (CMU 2015) and Musab Popatia, the co-founders of Stellic
By 2012, Stehlik had advised approximately 2,500 students when he accepted the job of Associate Dean for Education at Carnegie Mellon’s Qatar campus.
It was a rare opportunity to educate people in a different culture. Among the students Stehlik met during his three years in Qatar were Rukhsar Neyaz (CMU 2015) and Sabih Bin Wasi (CMU 2015). Frustrated with the difficulty of navigating course planning, especially as a first-generation college student, Bin Wasi walked into Stehlik’s office to complain.
And, as always, Stehlik listened. He shared stories of his own, and he became a life advisor, asking Bin Wasi and Neyaz: what was happening in their day-to-day lives? What did they want to do after they graduated?
As it turned out, what they wanted to do was create software that would help students chart out their academic journeys. It began as an independent project, to which Stehlik contributed. When the project became a company, Neyaz and Bin Wasi — now its co-founders — wanted to name it after him.
“He had done so much for us, and this was the least we could do for him,” says Neyaz who, along with Bin Wasi, was recently named to Forbes magazine’s “30 Under 30” list. They thought the app they developed would give other students on other campuses the essence of what Stehlik had provided to them: a compass.
His first impulse was to say no. Eventually, they arrived at a compromise — they could name the company after him, as long as they altered the spelling. This way, only those who knew Stehlik would get the reference. And so “Stellic” was born.
Now a Series B company, campuses across the United States are adopting the tool, including Carnegie Mellon. When Duke University began using it, Owen Astrachan told colleagues that he knew its namesake.
On Friday afternoons, if you were stuck inside, Stehlik wanted you going out to the Cut to play volleyball.
“It’s time to get out of the cluster!” he’d tell students. “Time to do something else. You can hack the rest of the weekend; give me an hour. Let’s go have some fun!”
Melitta (Andersen) Riley (SCS 2007), was one of the regular players. She’d been on her high school’s volleyball team, so Stehlik asked her to help him coach the volleyball program he started at his daughter’s elementary school.
“I could finally do something for Mark,” she said. “You would do anything for him, because you knew he would do anything for you.”
She met her husband, Matt Riley (ENG 2008, SCS 2008) while they were both undergraduates under Stehlik’s wing. Like Marcin Krieger, Matt spent Thanksgiving with the Stehlik family. When Stehlik selected him to hold the Computer Science flag during the commencement march from Wean Hall to the field, “It was one of the most profound recognitions I have ever had in my life,” he said.
Seven years ago, when their son was born, Matt and Melitta gave him Stehlik’s middle name — Joseph — as his middle name, to honor him.
In speaking about Stehlik, like so many others do, Melitta Riley’s voice breaks.
“It is a very powerful, emotional experience to be really seen and cared about,” she said.
Ian Voysey (SCS 2010), Researcher and Librarian
Ian Voysey (SCS 2010) was on and off academic probation constantly. A precocious guy, he kept taking difficult math classes, even when Stehlik advised him to stop because he wouldn’t be able to graduate.
Voysey responded by signing up for a second major in math, because he found it interesting, even when it was over his head.
“He said, ‘Voysey, you are my kind of stupid,’” recalled Voysey. “Which more or less sums up our friendship since then.”
Despite his own best efforts to the contrary, Voysey managed to graduate in 2010. Stehlik is the reason why. He was always pushing back on his students’ behalf: “It’s chaotic good, not lawful good,” is how Voysey put it.
After graduation, Stehlik got him work as a non-contract, part-time teaching assistant — something that did not exist, but Stehlik created for him. When the Introduction to Functional Programming course was split in two — a course Voysey had failed twice before earning an A — Voysey wound up rewriting half of it from scratch before moving to Qatar to teach its first offering on that campus while Stehlik was Associate Dean. “That’s a Stehlik timeline if I ever saw one,” Voysey noted.
Now both of them are back in the U.S., and they still meet for lunch once a month.
“I joke that Mark chose to downgrade himself from advisor to friend,” said Voysey, who is now a librarian in Helvetia, West Virginia, a town of 37 people.
“They broke the mold with him,” Voysey said of Stehlik. He worries about his friend: the toll that shouldering the problems of thousands of other human beings can have.
“I tell Mark I love him every time I see him,” he said quietly. “He knows.”
The 2024-25 academic year is Stehlik’s last as a full-time faculty member. He plans to return in a half-time capacity for another two years to mentor his students who are still moving through the program: “The finish line is important, and I want to be here for that.”
He also intends to have a say in his successor, to ensure the undergraduate program continues the way he has molded it for 40 years.
And though Stehlik’s legacy looms large, he will be the first to encourage and mentor his successor, letting that person know that they, too, are up for the challenge. It’s the same message Stehlik has delivered throughout his career.
Marcin Krieger predicts that Stehlik will, in retirement, go on a guest lecture tour, sharing his passion for students across the country and traveling to alumni events. He noted that Stehlik would have no shortage of influential former students to help him find speaking engagements.
“It’s really remarkable that somebody with so few aspirations can be that impactful,” Krieger said.
“But maybe that’s why,” he added. “He wasn’t doing it for himself.” ■
