When the obnoxiously loud bell signaling the end of first period blared over the high school auditorium P.A. system, Steve Blank perked up in his seat. "I remember this," he said, smiling slightly.

On Tuesday, Blank, the serial entrepreneur and creator of the Lean Startup movement, returned to his secondary school in New York City to speak in front of current students. He said it was his first time stepping inside Queens's Martin Van Buren High in 50 years--a number that prompted a few gasps and giggles from the audience of several hundred high schoolers. 

The talk was part of a series of fireside chats for students in BTech, a New York City Department of Education business program. Naturally, much of the dialogue revolved around business and Blank's experience as a student.

Asked what he wishes he'd known in high school, Blank said he wished he'd understood the importance of a simple ability: how to talk to people. 

While talking to other humans is clearly an essential life skill, Blank was thinking of it from a business perspective. As an entrepreneur, he told the students, you'll have to sell your ideas to people quite often. "You're going to have to learn how to get people excited about the things you're excited about," he said.

"In high school, they don't teach you how to look people in the eye and communicate," he continued. "I spent most days looking at my shoes. Maybe, on a good day, I'd look at some other people's shoes." 

The crowd of several hundred was surprisingly attentive for a group of high schoolers at 8:30 in the morning, at one point breaking into applause at the entrepreneur's advice to a student. Blank, dressed in a baggy sweater, khakis, and dad sneakers, kept the teens engaged with motivational quips peppered with occasional colorful language. 

"Every one of you can do everything you want. A couple of you will be millionaires. Some will be billionaires. Right now," he said, scanning the room, "some of you are saying, 'I feel sorry for these other poor sons of bitches, because that someone is me.'"

Blank, who retired from startup life after the $66 million IPO of his marketing software startup, E.piphany, in 1999, likes to say that if his high school class had had a "least likely to succeed" superlative, he'd have won.

One semester, Blank said, he earned four 65s on his report card--"mercy passes," he called them--and one 98. In that class, which he believes to be the first high school computer course offered in New York City, Blank and his classmates used the school's lone computer terminal to successfully hack the Department of Education's mainframe. "I found something I kind of liked about high school," he said. 

Throughout his career, Blank parlayed that interest into eight tech companies. Not all of them succeeded: In 1997, his gaming startup, Rocket Science Games, folded after four years in business. The failure lost the company's investors $35 million.

The same venture capitalists later agreed to give Blank $12 million to start the company that became E.piphany.

"If you don't own a failure, you can't fix it and you can never get better," he said Tuesday. "They knew I wasn't going to make those same mistakes again."