Avatar: the Last Airbender

"Aang and Katara are working tirelessly for peace when an impasse between Fire Lord Zuko and Earth King Kuei over Fire Nation colonies within the borders of the Earth Nation threatens to plunge the world back into war! Meanwhile, Sokka must help Toph prepare her hapless first class of metalbending students to defend their school against a rival class of firebenders!"--Publisher's web site.