The Klingon training academy was a school on the plant Ogat

In 2370, K'mtar, a gin'tak to the House of Mogh, suggested to Worf that he might consider sending his son Alexander Rozhenko to this school, where the instructors would make him into a Klingon warrior and prepare him for the Age of Ascension. Admission into this academy was most likely as Worf's brother Kurn was an influential man. This suggestion was rejected by both Worf and Alexander. (TNG: "Firstborn")