NEW YORK • Technically, the term "supermodel" predates the 1980s, but that is when we civilians first knew who they were: Linda, Naomi and Christy. (Evangelista, Campbell and Turlington.) Famously called the "Trinity", they were the first fashion models to challenge the celebrity of movie stars. There have been other supermodels since, but right now, none is as compelling as Karlie Kloss.

At 23, Kloss is leveraging her success as a model and large social media following (not to mention the reflected glare of her BFF-ship with Taylor Swift) into social activism for young women.

Through Kode With Karlie, Kloss underwrote 21 computer coding scholarships for girls in 2015. She has collaborated with Momofuku Milk Bar on Karlie's Kookies, a line of vegan cookies sold to benefit hungry children and other charities. Lest you think her a slacker, she began her freshman year at New York University (NYU) this month.

All of this made her a perfect lunch date for Turlington Burns, 46, who scaled back her own modelling career at its height in 1994 to go back to school. She graduated from the Gallatin School of Individualized Study at NYU and continued her studies at the Columbia University Mailman School of Public Health. Later, she married Ed Burns, the film-maker and actor, with whom she has two children.

In 2010, Turlington Burns founded Every Mother Counts, a charitable organisation dedicated to maternal health, for which she was named one of Time Magazine's 100 Most Influential People of 2014.

Over asparagus risotto and avocado salads at Il Cantinori, the pair discussed their surprising modelling careers, the effect on their families, and their shared commitment to education and improving the lives of women.

Philip Galanes: Christy, I love that you wrote Karlie a college recommendation.

Christy Turlington Burns: It was all about my crush on Karlie in 500 words. She is going to take this education and blow it up. She's so eager and ready and thoughtful about her next steps.

Karlie Kloss: The whole idea of believing I could go to college, and model, comes straight from Christy. It's a lot to take on, but she did it. But I may ask for help with homework.

Galanes: College is one of many similarities between you. Let's start with the way you were both "discovered" when you were just 13.

Kloss: You were 13, too?

Galanes: Some guy takes a picture of Christy on horseback, and another takes a shot of Karlie in a charity show at a shopping mall. Presto! You're models. Do you ever feel like you were plucked from childhood?

Turlington Burns: When I started working, it was just local markets. Miami and Northern California, where we lived. I was a regular kid with a normal family life. It wasn't until I was 15, on my way back from working in Paris, with my mom. We stopped in New York, and things really started to take off. But I had to go back to school. After that, I was back and forth a lot for work.

Kloss: It was pretty gradual for me, too. I was discovered at 13, but we lived in St. Louis, so I worked in Chicago. I did this Abercrombie Kids thing with (fashion photo- grapher) Bruce Weber. But he didn't even know I was there. The dogs were more important than me. It didn't explode for me until I was 15 and came to New York to walk for Calvin (Klein). Those runway shows can really catapult you. They put you in front of designers and top editors. And on the Internet.

Galanes: Fifteen is still very young.

Burns: But the stuff I missed, I'm happy I missed it. The social part of high school, I'm not cut out for that. I had a handful of great girlfriends, but my sisters are my closest friends. Some people just know: I need to go faster through this period. And I was ready.

Galanes: Had modelling been on your radar as girls?

Kloss: Not at all.

Turlington Burns: I hadn't even started reading Seventeen magazine yet. That's how out of it I was. But I have an older sister, and when we were asked about having our pictures taken, she thought it was cool. So, of course, I did, too.

Galanes: You started so young; you must have had a lot to learn about fashion and modelling.

Kloss: I had a lot of luck. I was the right girl at the right time. But I was also a sponge. I didn't talk a lot. I just listened and kept my eyes open and tried to soak up everything I could.

Turlington Burns: Fashion is all about references. All these names being thrown around. I was like: "Who's Anna Magnani? What's La Dolce Vita?" And I felt it was my job to learn them. It was an amazing education and fashion photographer Steven Meisel was a great teacher. We did so many movie screenings - with the hair and make-up team and Lori Goldstein, the stylist. Then we'd play: Let's do Sophia Loren! I also had a great experience with Arthur Elgort, the first big photographer I worked with. "Don't hold your hands like that," he'd say. I learnt so much from him about light and angles.

Kloss: Learning is what makes you better. I had the same experience with Arthur. He shot my first Teen Vogue story. And he loved that I could move. I had this ballet background. It's probably the biggest reason I have the career I have: I know how to move.

Galanes: You also had to learn about money. You were earning buckets of it as kids.

Turlington Burns: The money kept getting more and more. There was this thing where you signed a contract with Ford Models and tied yourself to them. And I was like: "No way! They work for me, not the other way around." The first time I signed a contract with Calvin Klein, they advised me not to have my own lawyer. My parents didn't know about that area. So I learnt by making mistakes and, eventually, I got savvier.

Kloss: I remember doing a shoot at Macy's after school. I got paid $700. The only comparison I had was baby sitting - at $6 an hour. Financial independence is empowering. And seeing a world that I certainly never knew existed. I don't mean the glamorous life. Seeing other cities, hearing other languages, tasting other food. But there's a responsibility in that, too.

Galanes: My favourite trick: You've both taken success at a job that's all about being scrutinised, objectified even, and turned it into a launching pad for projects that empower women.

Kloss: Christy paved the way.

Turlington Burns: I don't know about that. But I've always searched for ways to turn my losses into advocacy. When I lost my father to lung cancer, I said: "I'm not going to be photographed smoking any more. I don't believe in it." That experience was huge for me.

Kloss: I feel a responsibility with success, too. Like: Why wasn't it the girl next to me or my sisters? I've always worked with philanthropic groups. But I had my first "aha" moment when I was 16. I've always loved baking. I bring cookies to shoots. So I'm in this apartment in New York with my grandma, and I'm baking - because I can't go out at night - and I have this idea: Let's make a healthy version of these cookies and sell them to benefit hungry kids.Ten meals for hungry kids with every tin sold.

Turlington Burns: It's very human to want to make an impact, to contribute to the world. But it's hard to know the how and why. Like, "Will my small thing make a difference?"

Galanes: Was it important that your big projects - maternal health and coding for girls - be about equal rights for women?

Kloss: For me, it started with this realisation about how much we interact with technology every single day. No matter what you do. I wanted to know more. So I took this two-week coding class at the Flatiron School. And it was mind- blowing - like: "Whoa! This is how apps work; this is how my phone works." I thought, "I want to share this with other girls."

Galanes: Because coding is such a male-dominated profession?

Kloss: Like 80 per cent. It's very disproportionately male. That's why it's even more important to get girls involved. Technology and apps are the future, and I want girls to be a part of it.

Turlington Burns: We think about this all the time at Every Mother Counts. Could we come up with an app to connect mothers to one another and health providers? It's hard to dream when you don't know how things work.

Kloss: And if you understand the basics, you can understand the possibilities. So the call to action I put out there was creating access to coding for girls. Anybody interested in a scholarship, send me a video and tell me why.

Turlington Burns: To me, every life has equal value. I had a scary complication during childbirth. Later, I learnt that many women don't have access to the simple care that saved my life. That was a huge realisation. Every woman should be able to bring her child into the world safely. You don't need the best obstetrician, but you do need access to information and education.

Kloss: I feel really lucky to be a 20-year-old right now with my life ahead of me. I have opportunities that didn't exist for my mom and certainly didn't exist for her mom. I want us all to have them.

Turlington Burns: And when you surround yourself with people who are doing incredible things, they inspire you - your friends, your peers, your family - every day. They raise the bar for everyone.

Kloss: Can we have lunch together every day?

Galanes: After you finish your homework.

NEW YORK TIMES