Sith Apprentice is equivelent in rank to Jedi Padawan, although since Sith aren't indoctrinated from birth, they tend to be older and more powerful at the apprenticeship stage.  (A Jedi Knight who defects to the Sith can become either a Dark Jedi or a Sith Apprentice, although Revan and Malak were exceptions, mostly because they ducked out of the Sith power structure)<br/><br/>A student takes classes, and has their needs provided for by the Academy.  An apprentice serves under their Sith Lord, and has their needs provided for by their master.  The Master/Apprentice relationship is very intense and important.  Sith Academies are sometimes implied to be a survival of the fittest battle royale where the students simply kill each other in ritual duels until one of them gets chosen by a Sith Lord.  The Malachor academy also has the option of pursuing a dark side thesis, exploring some aspect of the force rather than trying to fight other students as a means of advancement.<br/><br/>(although at Korriban you can loot an ancient temple, or if you're really bold, pull a sociopathic practical joke to prove your superiority)