It doesn't really matter if the idea is good (seems original to me) or if you can actually map the school. A HL2 mod with your description won't work unless you have the necessary models and skins to make all those "nerds", "chicks" etc. Are you planning on using the standard npc_citizen models for that? I'm not sure that would work either...
For anyone who wants to make a mod, my advice is to ask yourself some basic questions:
-Do you have an idea of the scope of the mod? (how many maps will it have, how long it will take to make them, etc)
-Do you have the resources (models, materials) needed for your theme, or at least, the time and skill to make them?
-Is your idea enough to interest serious level designers?
-Will your inspiration to make the mod last or fade away?
I'm saying these things because I was working on a mod years ago, and my answers to some of those questions were negative. I haven't started any big projects since then, or the ones I tried just failed