The Farseekers by Isobelle Carmody
Since their takeover of Obernewtyn, Elspeth and the Misfits have been preparing for the inevitable confrontation with the Council - developing their forbidden mental abilities so they are ready for battle. But in the midst of plans to rescue a powerful Misfit, it is foreseen by a futureteller that the fate of Obernewytn is inextricably bound up with their quest. Led by Elspeth, whose extraordinary powers set her apart from her Misfit friends, the expedition sets out on its danger-filled task.