Batman: Arkham City Concept Art
Although a lot of fantasy RPGs have similar themes and tropes across the board, several of the more high-profile retroclones emulate more than straight mechanics of earlier Editions. Lamentations of the Flame Princess, Spears of the Dawn, Astonishing Swordsmen & Sorcerers of Hyperborea, and Dungeon Crawl Classics among others are inspired by unorthodox styles. For this new series I plan on covering each of these RPGs (and potentially others), discussing how the game lends itself to a magic school campaign.
Lamentations of the Flame Princess is a Basic D&D (Moldvay B/X) retroclone with several notable changes to make it more in line with a weird fantasy vibe. Dungeons are truly horrific places full of things which shouldn't be. Adventurers are social outcasts who tend to be either forced out of civilized society, or have nothing left to lose to take up such a suicidal occupation. Inscrutable cosmic forces of Law and Chaos guide the hands of spellcasters, with both sides being just as inimical to mortal life and welfare. While it is true that Clerics gain their spells through prayer and formal rituals, there is no concrete proof that the deities they serve are what they appear to be or if they even exist. The craft of the Magic-User is an art, not a science, the arcane notations within spellbooks meant to trigger a dream-state so that the mortal mind can be temporarily altered to accept the spell knowledge. Naturally, weird fantasy magic academies are going to carry about an air of the macabre.
If the school caters to Clerics, it will not be the typical bright and holy shrine of shining goodness: even if their cause is just, the trials necessary to make a proper Cleric are harrowing and many initiates who fail end up broken, harrowed shells of their former selves. This is accepted as the price to pay, whether the faith is on a war footing with evil powers or the church serves a vengeful god who tolerates no signs of weakness. Old priests, broken and scarred by their encounters with the darkness, tell harrowing tales of what awaits beyond the confines of civilization and the light of Law to a classroom of junior witch-hunters. Druidic cultists gather in the rootways and tunnels of giant seed-monoliths; there they commune with the Horned God and breed strange amalgamations of nature and other divine 'gifts.' Warrior-monks living in sequestered communes stand stalwart over the prisons of sleeping abominations, their children and children's children passing on the secret blessings so vital to maintaining the wards which trap the beasts.
In fitting with their connection to Chaos, schools for Magic-Users are less scholarly and ritualistic than their divine counterparts. The tomes of arcane knowledge read less like an academic treatise and more like drug-induced, stream of consciousness writings put down by spellcasters trying to make sense of phenomena they can never truly understand. Spells are not divided into categorical sub-groups of alteration, divination, and the like. Spells by their very nature are the anti-thesis of worldly knowledge.
Schools of sorcery are scorned by most civilized realms; some of them are not schools so much as hidden cabals masquerading among a more mundane college. They might be cloistered pseudo-prisons in the ghettos of a vilified ethnic group, the mages' threats of terrible magic the only thing holding the angry mobs and crusading knights at bay. They might operate openly in cities secretly ruled by inhuman abominations beyond the stars, who force magically gifted children into their cyclopean cavern-cities for their own nefarious purposes.
If the Referee allows for all character classes in a Weird Fantasy school setting, then no further adjustments should be made. The noncasting classes then serve as an auxiliary role to the true spellcasters of the academy. Dwarves and fighters might be part of a vigilant knightly order tasked with the grim job of slaying any student who gets corrupted by fell powers, and possibly to defend their charges from rogue summoned entities. Halflings might be servants and staff who help with the daily chores and upkeep of the school, while specialists might round out the more practical teaching positions which supplement the magical arts.
But if the Referee seeks an all-caster party, whether a mixed group of clerics, elves, or magic-users (or an academy with only one type of class) several factors must be considered. Unlike other campaigns for Lamentations of the Flame Princess, the party will not have access to the martial mastery of a Fighter or the diverse skill-set of a Specialist. This is understandable to a point, as in a typical LotFP campaign fights are dangerous, bloody affairs to be avoided if at all possible.
For ability scores, I recommend doing the 3d6 method, with the exception of the abilities of primary importance to said class (Intelligence for Elves and Magic-Users, Wisdom for Clerics), in which case 2d6+6 is rolled for said ability score. That way it's highly likely that the PC will end up with at least passable expertise in spellcraft.
On the fighting front, elves and magic-users gain access to some potent offensive spells such as Magic Missile, Sleep, and maybe even Summon! The possibilities at higher levels only increase. Clerics are not very good offensively, but the Bless spell can be allocated for to-hit rolls, and they're very adept at fighting undead.
For skills, I recommend taking inspiration from the demi-human classes and allowing each PC to have a 2 in 6 rating in a single skill of their choice. This rating increases by 1 at 4th level and every 3 levels thereafter (to a maximum of 6 in 6 rating at 13th level). The chosen skill must be explained as being somehow related to the apprentice mages' arcane studies, the weirder the better. Architecture might be gained through dreaming visions of five-dimensional realms beyond space and time; Bushcraft might be gained via pacts with primordial entities sleeping beneath the earth; Stealth might be earned when the mage gives away his true name, family ties, and eventually all aspects of his identity to truly be forgotten and master the arts of illusion.
For experience, the Referee might substitute treasures for supernatural knowledge with an arbitrary silver piece value (to convert to experience points). Perhaps the party needs to obtain the eggs from the primordial ooze-ponds to serve as a material component for a ritual. In order to complete the Trial of Thorns beneath the Witch-hunter's academy, the party might first need to prove their mettle to the school's quartermaster who supplies apprentices with silver weapons and holy water. The PCs do not quest for the crude pleasures of wealth, but for the strange and macabre artifacts so necessary to further their own power.
In conclusion, a weird fantasy school campaign should focus less on the wonders of magic and more of the dreadful fear of what it does to people. Magic grants power, but it does not grant freedom. Schools are claustrophobic prisons of forsaken men and women who can never go back to their old lives. And nobody, not even the teachers, can be trusted to look after your welfare.