Is XNA Game Studio too much for High School students? Not if they are motivated!
Case in point is a project by Amir Shah, a 16 year old junior at Springbrook High School in Silver Spring Maryland, who is working on Pong for the Zune. (http://amir.shah.org/index.php/archives/165 )
Another example is Brian Scarbeau a high school teacher in Orlando Florida who has been posting videos of the XNA products his students have been doing (http://geekswithblogs.net/bscarbeau ) as well as lessons learned from his first semester teaching XNA to high school students. Brian is one of about 11 high school teachers I am in contact with who are teaching with XNA - some only as extra projects for the top kids but some as a specific course in game development.
Infact, when a co-worker went to visit Brian, he showed the student games that were amazing. They took the basic concept of a 2d shooter and added their own creative twists - some involved game state, level advancement, etc. without being handheld or forced to go in a particular direction. It was gratifying to watch 9th graders debug and modify C# like pros, and become passionate about the work they did when explaining how their game worked to me.
Really awesome to see that XNA *CAN* be used effectively at this age level; even though it's meant for the general enthusiast.
Another graduate high school student (16 or 17 years) present a project for the local Imagine Cup competition this year in Russia. What he did is a 3D gaming environment coupled with some physics simulators like Bullet and Newton to create realistic behaviors of game objects. He is not exactly a good example of what an average school student can do (he is too geeky for an average student), but rather a demonstration of how far can a person of his age go.
XNA Game Studio for the Zune is basically 2D gaming using SpriteBatch. Indeed, learning to write games using SpriteBatch is the BEST way to learn XNA Game Studio, for students that are ready to handle the task of writing C# code. Indeed, even for people that don't have a Zune, it's quite easy to "emulate" the Zune limitations on a Windows PC. In fact, many laptops that would normally not be able to handle the 3D features of XNA Game Studio would hold up very well to games that are limited to simple SpriteBatch-based games!