Aura wrote...
Well, first of all I'd choose the setting more carefully than "Japanese high school". :P
The structure of a visual novel allows so much more than a traditional book, so that's where I'd look next. Interactive storytelling does not have any well understood theory yet, so it's very hard area to explore for an amateur writer. I'd especially would like to break away from the "path/branch" line of thinking. Here's an interesting article about the subject: http://gwsig.quantumcontent.com/?p=13
Third area is presentation, but it's an area where amateur budget creates an impassable wall. Visual Novels are produced with the same mentality as animation, maximum reusability and cost saving being the priorities. This means that same sprites, camera angles, locations and characters will repeat themselves endlessly over and over. As the best example to the contrary: Littlewitch's
Quartett broke radically away from the traditions of visual novel presentation with its FFD engine, with magnificent results. The game looks like an coreographed slideshow animation of a comic book with background music and voice acting. It's one of my favourite visual novels ever, but something like that would be impossible for 4LS to make.
Regarding interactive storytelling, I'm surprised that there isn't much theory around. While the "visual novel" medium has been poorly explored in the West, there's certainly no shortage of interactive storytelling in the past few decades. Choose-your-own-adventure books have been around for at least decades (five seconds on Wikipedia wasn't enough to even pin down a date range, and literary history isn't exactly my strong point), and with the advent of computers, there's been a great deal of text-based or point-and-click adventure games, which are probably one of the ancestors of the visual novel (though by no means the only one).