By the time he was in his 60s, Dave Thomas was a household name and his fast food franchise, Wendy's, was the third-largest in the world, behind only McDonald's and Burger King.

A high school dropout, Thomas, who died in 2002 at the age of 69, proved that he didn't need a degree to become a successful businessman.

But he also knew that his success might encourage young people to quit school.

So at age 61, more than 40 years after dropping out, Thomas re-enrolled as a student at Coconut Creek High School and earned his GED in 1993. He became an education advocate, saying that dropping out of school was one of the worst mistakes he'd made in life.

Thomas later founded the Dave Thomas Education Center in Coconut Creek, Florida, which offers GED classes to young adults and is a part of the Broward County Public School District.

It's interesting to note that those who drop out of high school — like Thomas and David Karp, founder of Tumblr — advise young people to carefully consider their choices before making the same decision.

But it's more difficult to find successful dropouts who support students finishing their college degrees, and rising college costs and non-linear career paths have actually encouraged a handful of people to speak out against attending college.

Richard Branson, a high school dropout, has spoken out against the university system, saying racking up student loans is "completely unnecessary" and suggesting that schools "re-think" their courses to get young people into the workforce more quickly.

And PayPal founder Peter Thiel (a graduate of Stanford and Stanford Law School) is paying 20 students $100,000 each if they start a company.