Enable Interactive has been chosen to create the social networking site, marking its third project for the charity in recent months.
A key element of the site is that it will be a secure social network, with teaching assets to help introduce, educate and involve children in activism.
The network will be used by teachers during Citizenship lessons for 14- to 16-year-olds, initially in a small number of schools, with rollout to other schools in the UK across 2008.
The aim is to inspire students to campaign on a range of issues that they feel passionate about by writing to their MP, taking part in polls and quizzes, organising events and joining or creating online groups.
Children will also be able to use the network out of school to keep in touch with their friends to discuss issues and encourage others to take action.
Will Lord, online campaigns manager at War Child, said: "This is the third project we have worked on with Enable and believe that they are the best people to help us engage with this young audience.
"They're incredibly creative and genuinely passionate about what War Child does and what it is trying to achieve."
Matt Connolly, strategy director at Enable Interactive, said: "By tapping into the social networking trend, War Child Schools can educate and motivate children whilst being in a safe environment that is familiar to them.
"War Child has an amazing ability to cut through and communicate with its audience at their own level."