Knight School is the academy where people can train to be knights as mentioned in King's Quest Chapter: Adventures of Graham. It lies to the far north possibly in the nation of Llewdor (KQGS) (though there maybe more than one institution, and perhaps in other nations as well).
It is said that potential knights could improve themselves and catch up with experienced Knights by taking extra Knight School classes. It has made huge differences for some knights.
It is a school of higher learning in a land outside of Daventry. While attending the academy he tried to find knight jobs, but career opportunities had all but dried up. Coming to Daventry was his last chance.
It may teach defenses against magic as Graham seems to know a lot of about potions, spells, and other magical recipes (including transfiguration elixir, invincibility potions, understand the language of creatures, sprout the wings of an eagle or a fly, teleportation at random, summon a storm that follows you, transform into a cat/clawed feline). Though he does not specifically seem to be expert practitioner of magic himself, he shows some promise at alchemy.
Behind the scenesEdit
In new King's Quest history, Graham never grew up in Daventry instead he lived in Llewdor or some unpronounceable land where his family had been a long line of protectors of crowns (both knights and dentists). The land appears to be within a half-day's journey from Daventry (as he had eaten breakfast with his mother that morning).
In this version of history, he never attended Edward's Palace School, Daventry High School, the Royal University, or Daventry Knight School.
This is both a pun, and perhaps a reference to the Knight School mentioned in Hoyle's Official Book of Games: Volume I, which at least in the original series is one of the schools Graham is said to have attended. There is no way to know if this was an intentional reference to Hoyle 1 reference, and considering its a great 'pun' it might just be a coincidence.