FF: Did not exist in the game.
FFII: White Magic, though it's calculated using the same formula all Black Magic is.
FFIII: Did not exist in the game.
FFIV (Series): White Magic and Black Magic. (In The After Years, Golbez could also cast it with Cecil.)
FFV: Did not exist in the game.
FFVI: Hard to classify as Terra learns it at 99, and learns both White and Black Magic naturally (without Espers). Ragnorak and the Paladin Shield both teach the spell, and while I can see an argument that a Paladin Shield would teach White Magic rather than Black Magic, it's not quite enough since it can be worn by anyone except Umaro. Ragnarok also only teaches Ultima so it's not really possible to draw much of a correlation from that.
FFVII (series): Unclassified, and all magic is learned through Materia and not really broken down into schools, and each character can learn each type of magic.
FFVIII: Also unclassified, as it's drawn, and everyone can use it.
FFIX: Also unclassified. Only Kuja can use it, and he has both White and Black Magic spells, also it's only a story element, used to end battles and in a cutscene.
FFX (series): Black Magic.
FFXI: Does not exist in this game (yet, at least).
FFXII: Does not exist in this game.
FFXIII: Black magic, only Barthandalus can cast it, and he only casts Black Magic.
FFT: Unclassified, as it's a Squire ability, though the closest argument for a school of magic would be Blue, since that's the way it's learned.
FFTA (Series): Unclassified, it only appears as weapon skills.
FFCC: Unclassified, as one must combine White and Black magics to get it.
Doesn't exist: 5
White Magic: 2
Black Magic: 3 (2 if you want to say that Golbez's ability to Band it doesn't count.)
Blue Magic: 1 (If you want to say FFT's version is a particular school.)
Unclassified: 7
White Magic is at best tied with Black Magic for the school, at worst behind it. Ultima is a powerful spell that SE (just Square in older times) adds in whichever way best suits the game (in their opinion at least) in question.