Barbarians: Not necessarily savages, but certainly the more aggressive of combatants. Military personnel can still be Barbarians in class, you can still be civilised, but you simply have this aggressive, spiritual aspect to you.
Bard: There are no colleges as institutions, but there are schools of activity in the sense that there is a recognisable style. Individuals seek out a patron or teacher and either cultivate their own style or they learn that of their mentor. Respected as historians and advisors as well as entertainers, Bards hold cultural significance in the worlds of the Taihun.
Cleric: Idols and symbols play a large role, and the churches in many places represent the government. This isn't a world-wide certainty, and many kingdoms have churches as simply small community centres for the citizenry, but faith and worship certainly has hold of the world.
Druid: The Druid Order is a single centralised organisation, unlike the Churches of the clergy that worship, mostly, the Taihun as a collective. While Clerics are very localised, the Druid Order operates as a worldwide plane-spanning group that tries to address larger concerns. Often distant from individual kingdoms and disputes, trainees and those looking to move up in the Order are encouraged to travel and learn from the world in which they live, hoping for a jaded disdain for petty politics to set in.
A person can join the Druid Order without being a Druid by taking the Druid Order Initiate background package, but one cannot be a Druid without also being part of the Druid Order.
Fighter: Similar to Bards, there are no Fighter Colleges or the sort, but there are patrons and teachers. They often are former militia or war veterans. Few kingdoms have standing armies, and those that do tend to keep their training in-house and don't allow outsiders or deserters. If you're a fighter, you're likely to either just be really observant and learned on the job, or you've been trained by a single person.
Monk: Like martial artists in stories, these are the warriors of great supernatural talent. Remote monastaries, aged individual teachers hiding in a village, and those self-taught guided by spirits and voices in the night; these are the sources of a Monk's training.
Paladin: … Same as the book, pretty much.
Ranger: Whether a small town huntsman or a learned trader that journeys great distances, Rangers are able to look after themselves and others out in the wilds.
Rogue: These are not your small-time thieves, but rather your trained Assassins and Dungeoneers. Small cabals in large cities will train in candlelit tunnels and alleyways, or self-taught adventure seekers diving into the dark caverns of long dead kingdoms and learn very quickly when to duck, where to land and how quiet to be.
Sorcerer: Same as the book.
Warlock: Same as the book.
Wizard: There will be small groups of very ancient wizards that might be convinced to take in promising students, but mostly they are self-taught over years by combing through tomes in dusty libraries. A few wizards have stumbled upon Power Monoliths, large structures placed by an ancient civilisation long since forgotten. These Monoliths count as a spellbook. While not transportable, access to a Monolith grants access to the spells within. This often means Wizards set up small strongholds around these constructs and rarely move, while a few travel to find others, seeking their origin and how to copy their magic down into a portable medium.