Swinburne University of Technology in Melbourne have created a free 2D game development kit called Swingame.  It is designed for beginner programmers and is easy to use, powerful and fun.  You can use it to create games in Pascal, c#, or Visual Basic. 

There is a tutorial called VBugs for Swingame that is particularly aimed at teaching year 9-11students VB.Net.  It walks them through the process of creating a game called "VBugs" and shows how to use sprites, sounds, mouse and keyboard input, along with developing procedures and designing classes.

There are FREE downloadable teacher and student resources including lesson plans, worksheets and activities.