Alison Daniel-Cutler of Google's pre-university education team writes:

Code In is Google's contest to introduce pre-university students (age 13-17 years old) to the many kinds of contributions that make open source software development possible. It runs from November 21, 2011 to January 16, 2012. We invite students worldwide to produce a variety of open source code, documentation, training materials and user experience research for the organizations participating this year. Find out more about tasks here and take part to be in with a chance of winning some great prizes!
Launch blog post: http://google-opensource.blogspot.com/2011/10/google-code-in-are-you-in....
Further details: http://code.google.com/opensource/gci/2011-12
Code-In contest website: http://www.google-melange.com/gci/homepage/google/gci2011

We’re looking forward to a fun contest this year and hope you’ll participate yourself if you are eligible or spread the word to friends, family, and colleagues about the program.

If you have any further questions please email the contest discussion list and one of the contest administrators will be happy to point you in the right direction.