Bottom-line, you need experience. I'm young, 22, but got my job as lead developer when I was 20 and in college because no one could argue with my experience. I don't mean you need to go and work for a dozen companies before you can get a job where the founders trust you. Do what I did, manufacture experience. I've written around 10 medium-large scale projects by myself, one being a social network that wowed the founder of my current company.
One thing I know for sure, school means almost nothing. It helps a lot but only when you spend the time learning as much as possible about web technologies. As well as developing and refining your skills as a web developer.
That is precisely what I have been doing. I spend considerable amounts of time learning about web technologies and refining my skills, and it really has nothing to do with making myself employable. On average I would rather experiment with Seaside than play a video game.
I am 21, and actually already have considerable experience in the work field so far, but have been unsatisfied. I think I would find a startup much more to my liking. Perhaps I will have to follow your lead and develop a pet project into something impressive.
One thing I know for sure, school means almost nothing. It helps a lot but only when you spend the time learning as much as possible about web technologies. As well as developing and refining your skills as a web developer.