My answer has always been "no." Read this post, from a venture capitalist.
there are two ways to build a company.
You can design it from scratch, figuring out exactly what you want to build, getting it all down on paper, raising some money, and then building it. And there are plenty of success stories for that way of building a company.
Or you can just find yourself doing a startup because something you started as a hobby, or to serve your own needs, just took on a life of its own and you have no choice but to evolve it into a business.
The "intelligent design" approach is what gets taught--how to write a business plan, and so forth. The latter approach--evolving the business--appeals to me more.
I've always felt that going to business school was a substitute for being an entrepreneur, not a complement. Those who can, sell. Those who can't, sit in class.
In my own book on entrepeneurship, Under the Radar, I use the phrase "learning by selling." I think that trying to get somebody to pay for something is the most educational experience you can have, at least if you want to be an entrepreneur.
My hypothesis is that most entrepreneurs would rather do anything than sell. Design a cool product, yes that's fun. Make fundraising pitches to investors--well, it's no fun getting turned down, but the ritual itself is stimulating. But selling? Dealing with suspicious, unpredictable customers? It's obviously necessary, and yet you'd be amazed at how easily entrepreneurs talk themselves into avoiding it.
And, in my humble opinion, taking a course in "marketing" (business schools do not even want to use the "s" word) is one form of avoidance.