No matter which way you slice it, students are more engaged when the "real world" is the focus of their learning. Getting kids to write for an authentic audience is one of the best ways to make this connection.
To get them started, websites like Youth Voices and Tween Tribune provide vibrant online communities to make meaningful connections with fellow young writers. Kids can also get some direct experience in critiquing and receiving feedback with TeenInk and LitPick. For those especially interested in real-world topics and current events, The Learning Network and KQED: Do Now are chock full of activities and prompts to get kids reacting and writing. With any of these tools, kids will write with passion and purpose as they learn the value of written communcation outside the classroom context.