I'm not sure if this has been asked yet, so I'll go ahead and do it now.
For the arcane schools special powers, are they dependent on character level or caster level? I've gotten the impression that you get the abilities based on how many levels of wizard you have, but the explanation in the Spells section of the book is a little bit unclear; it lists the abilities being gained by caster level (for instance, for conjuration you get Acid Dart at first, Dimensional Steps at eighth, and Summoning Master at twentieth).
Sorry for asking a silly question, but I wanted to make sure.