Hi George,
I am the same age as you and if you are interested, I wrote a screenplay a few months ago. Like you, I wrote it keeping my lack of locations and actors in mind.
I believe if you were to film it, you will have no trouble. Some effects are needed, such as the basic gunshot effects. They are not too hard to achieve (the effects in the film in general) and I originally planned to film them using different techniques to make it even easier.
I trust that it will fit most of your expectations.
Genre: Crime, Drama
Casting: Around five teenagers
Locations: Inside the school (classrooms) and some scenes with anywhere outdoors
Length: Roughly twenty minutes
Effects: Basic; tutorials can be found online
Budget: Zero to a few bucks
Instead of wasting your time reading the entire script (should be about 20 pages), I will summarize it. Parts of my script was inspired by Pulp Fiction, and an alternative scene suggests references to the film even more (I replaced that part though). To begin with, I always thought films with teenagers and guns were bound to be corny and unrealistic, so as a challenge, I wrote it so that this seemed more believable. The idea is, two girls go to one school, and aim to sell a particular drug to the teenagers there. However, up until the end of the film, it is not revealed what they are selling. As these two girls go to the school, we are revealed of a few different groups of characters. The most important ones: Two students, both addicted to the drug, aim to stop the two girls from selling it. Two boys, who are from a completely different time frame (scenes with them are from the future) discuss the outcome of the two girls selling drugs.
There is an overall confusion to some parts, but as it progresses, I believe the story will be more revealing. A second viewing could even be necessary.
I was going to film this but did not have enough time. Just tell me if you are interested and I will gladly send it to you.