Weeeeell,
In my opinion and from personal experience, I am going to have to agree with some of you and disagree with some of you as well. Sorry

Reading on your own is definitely cheaper, but requires discipline. Also, there is something about mingling with fellow humans. It's called socializing. You get to rub shoulders with diverse pples, learn from them, network with them. If a school environment weren't necessary, y r so many people taking jamb 10 times just to go to the university?
Having said that, just because Temitope puts up a sign outside his shop along Ibadan expressway doesnt make him a good teacher. As they say in the states, those who can, do and those who can't, teach

Obtaining a certification doesnt guarantee you a job or success in your career.
As I said, those who can't (as in those who arent willing to swim with the sharks in a capitalistic society) tend to teach, *generally speaking*. Some who teach do it because they can't interact with people in the real world. There are people born to help others, those born to do research, those born to live the comfortable life, and those born to take risk and hopefully reap the rewards tenfold.
To the person who said he should get a laptop and buy some books, what if he doesnt have the resources to obtain such? Even for a free ebook, it still requires time at a cybercafe at the very least. You can only learn so much for N100 or so an hour.
To the one who asked y those who are teaching arent making money off the many people wanting websites, could it b because they are making money off of those who come to them for teaching?

I personally would want to teach in some capacity. After my many years of experience, and not to discourage any of you, quite frankly, web dev is getting boring. All it takes is for you to come up with enough code in your library that soon your work becomes nothing but cut and paste. That's been my experience anyway. Trust me, I have grown gray hair in the biz

To summarize, I would go for a blend of both - attend a class, then solidify what you have learnt via self-training. Follow that up with giving yourself coding assignments, go work for someone to gain the experience/connections and/or work for yourself. Thanks to sites like scriptlance and ecoder, there should be plenty of work out there for you to get your feet wet.
As always, my 2 cents