Leave Harvard with an MBA and you can expect your first annual pay check to be around $130,000. You'll get about $50,000 more in signing and other bonuses, and you'll be well on your way to a high-paying career. Even if you decided to skip the cash and head for the non-profit sector, your annual pay would still likely be about $90,000 per year.

Of course, you don't have to go to Harvard to land those benefits. A report in the Financial Times in 2015 found that three years after completing their courses, all MBA graduates were earning an average of 90 percent more than they had earned before they had started business school. Even students who were older than 31 and had already worked their way up the management ladder before returning to school, earned about 63 percent more after graduating. In dollar amounts, spending two years studying for an MBA should send a student straight into a six-figure salary.

That's just as well, because the 100,000 MBA graduates that business schools produce every year could each have paid as much $65,000 a year in tuition fees alone. Even with those big starting salaries, it will be some time before an MBA graduate pays off their debts.

But what lands those six-figure incomes may not be the knowledge that MBA students pick up in the classroom. It could be the selection process that business schools use when they pick their students. For corporate human resource departments, the school will already have done the hard work of picking the best candidates. An earlier article in the Financial Times quoted one expert who recommended that people apply to business school, land the offer, but save their money by turning it down. Just being able to tell an employer that you were accepted by Harvard Business School should be enough to land you that big salary without having to sit through hours of case studies or spending a fortune on tuition.

So if your goal is to earn six figures within the next five years, than applying to business school could well be a good move. The school will show employers that you've got what it takes to lead and succeed. The knowledge that you pick up in the classroom will probably turn out to be useful. The contacts you pick up in the classroom certainly will be.

But two years of case studies and all-nighters isn't the only way to give yourself a big pay rise. My income picked up not when I went to business school (I didn't do that). It happened when I left my employer and went to work for myself.

It happened when I believed that I really could make a business work alone.

It didn't happen immediately. There was no graduation ceremony. I still had to network, but I did it at conferences instead of in the classroom. I still had to study, but I studied the things that I was really interested in and that I believed would be useful. I still received grades but they came from real customers instead of from professors.

Business school will teach you a lot. It will show you how to be more efficient and productive and a better manager. But that drive to be an entrepreneur? That has to come from you... and it's worth more than an MBA.