The feat Apprentice (Dungeon Master's Guide II 176 but the full description spans 175-9) says that
Once the apprentice reaches 5th level, he graduates from his apprenticeship. He continues to gain the benefits of the Apprentice feat, but no longer needs to work with his mentor. The mentor’s associated skills remain class skills for purposes of determining the maximum rank he can have in those skills, and he still retains the secondary benefits, but an associated skill can only be purchased as a class skill if he gains a level in a class that has that skill as a class skill. He no longer needs to tithe to his mentor upon gaining levels. (178)
Does a creature with 5 or more racial Hit Dice graduate automatically upon entering play?
"Who cares?" The Dragon #297 epic feat Battle Dance (29) has as a prerequisite Perform 30 ranks, typically putting the feat out of reach of an upcoming campaign's big bad, a 50-Hit-Dice leShay. (Its maximum number of cross-class skill ranks are only 26). The feat Apprentice makes the skill Perform a class skill, but graduation from the apprenticeship immediately upon taking the feat Apprentice means paying 60 skill points for those 30 Perform skill ranks instead of 30 skill points, a not insignificant amount given that the leShay must already spend cross-class ranks on Balance, most Knowledge skills, Spellcraft, Tumble, and Use Magic Device! I am aware of other effects that make skills class skills—I'll probably use the Dragon #326 anarchic feat Flexible Mind (80) for the skills Tumble and Use Magic Device, for instance—, but a leShay's Apprentice feat's ability to also possibly find level 25 admirers is an awful valuable resource!