Comment UDK and a few other options (Score 2) 237
Speaking as a current indie & AAA gamedev who has built game-related curriculum for 3 schools (middle school through college)...
Because of the diversity of student types (artist vs game designer vs programmer, etc...) I recommend teaching EPIC's Unreal Development Kit (UDK).
The tools are mature and will immediately offer something to every role on a game project.
As for yourself, the UDK uses Unrealscript which is based on a C++/C# syntax.
There is a wealth of knowledge via books and internet tutorials. (e.g., Just typed in "UDK tutorial" in YouTube and received over 4500+ results!)
A nice bonus is that learning UDK is something the kids can actually put on a resume and/or help them get an internship.
Milage will vary with other pre-built gamedev environments.
Below are a few all-in-one-solutions that have editing features, based in a Windows environment:
App Game Kit (AGK) - http://www.appgamekit.com/
Construct2 - http://www.scirra.com/construct2
Game-Editor - http://game-editor.com/
Game Maker - http://www.yoyogames.com/make
Game Salad - http://gamesalad.com/
Scratch - http://scratch.mit.edu/
Good luck!