Some schools have dedicated drama departments. Some schools even hire full-time technical directors to oversee the necessary carpentry, lighting, costuming, and props work for each theatre production.
And then a whole lot of schools simply dump directing responsibilities on whomever they can find among their faculties to volunteer. This post is for any such volunteers who may, at one point or another, find themselves in a little over their heads as far as the technical aspects of theatre are concerned.
Surprisingly, there aren't too many good informational pages for stage carpentry on the web. Most tech. theatre sites are aimed at semi-professional or professional groups, rather than high school drama clubs. Flat Building 101, however, is welcome exception, especially if perused in conjunction with Ben Teague's more diagram-heavy How to Build a Flat: An Illustrated Guide. Teague's guides to platform and stair-building are also extremely informative, with lots of step-by-step advice.
Remember, measure twice, cut once!
For lighting, take a gander at the Stage Lighting page at theatrecrafts.com. Lots of useful diagrams of different instruments, as well as advice on how best to configure your lighting plot. If you're a complete lighting newbie, however, you might consider purchasing a more comprehensive how-to book, like the well-reviewed A Practical Guide to Stage Lighting or Designing with Light: An Introduction to Stage Lighting.