It may seem silly for an Inc. 500 owner to head back to the classroom. But for most entrepreneurs, especially early-stage types, building and sustaining a business involves constant learning, says Wendy E.F. Torrance, who leads the Kauffman Founders School at the Ewing Marion Kauffman Foundation in Kansas City, Missouri. What kind of learning? "Most anything," explains Torrance, "that helps you master what you don't already know." Inc. asked her to tell us more.

Why bother with school? Inc. 500 company owners run successful businesses.

Well, even the most successful business founders have knowledge gaps in areas such as sales or finance. Those gaps can hinder the growth of their business. It also helps to know something about marketing, for example, if you're looking for a chief marketing officer. That's where the classroom can help. Noam Wasserman of the Harvard Business School likes to point out that a good teacher or mentor can help you learn things you don't know you need, but that you may need in the future. That's lost on some people.

How the heck would entrepreneurs find the time to go back to school?

There are professional development courses--online and on campus. Many business schools offer classes in the evening. Executive education programs can be pretty flexible. If you're between businesses, you've got plenty of time, even for a degree.

Seems as if online might be the best way to go?

It does have its advantages. You can hang out at Starbucks and get the job done. You learn what you need to know when you need to know it. The downside? You have to be more self-directed and able to reflect on and implement what you've learned without a teacher always standing right over you.

If you're smart, you'd take what you learned online and reflect on those lessons with mentors and advisers like your board members.

Are there any advantages to going old school and taking courses in person?

Well, in the classroom, a teacher will ask probing questions and hold you more accountable. You get a little of that online, depending on the course, but obviously not as much. You also get more feedback from people in other industries with different backgrounds, and you can exchange ideas with other students.

In our survey of Inc. 500 company leaders, only 38 percent said they attended grad school, and only 21 percent recommended that would-be entrepreneurs do so. Doesn't that argue against more education?

I understand those arguments, but consider this: Last year, Aileen Lee, founder of Cowboy Ventures, identified almost 40 tech companies that were founded in 2003, with values of at least $1 billion. Then, Jeff Bussgang, a Boston VC, and Harvard Business School student Juan Leung, in a separate project, took that data and evaluated the educational backgrounds of the founders and executives.

In The Huffington Post, they revealed 33 percent of the companies had at least one founding member who had an M.B.A. More than 80 percent had at least one founding member or current executive team member with an M.B.A. Examples included Kayak, Yelp, and Zynga. That says a lot, I think.

OK, so an M.B.A. isn't such a bad idea. But one size doesn't fit all, right?

If you are going back to school with the idea of starting a company, you really have to consider the culture of entrepreneurship at that program. A survey of alums at MIT who founded companies concluded this: The network of current and former entrepreneurs associated with MIT--who support current and former students--is a critical influencing force in the founding of companies. This was true for 1950s graduates and is even more so today.

Then there are the courses. The University of Chicago teaches Entrepreneurial Selling. Harvard has its Founders' Dilemmas course. Schools such as University of North Carolina and University of Michigan have very vibrant entrepreneurial programs. In other words: The school should have the right courses and the right networks for entrepreneurs. If the college you are considering doesn't have those attributes, you may want to look at another M.B.A. program.