All right, haven't read the Quintessential Fighter, but here's essentially how it works in the Scarred Lands Fighters and Barbarians Guide.
There's about 3-4 pages that detail the major schools of Clayborn, Hammerdale, Plague, Glamerhill and Wake. Each takes up about half a page. Following that are about 3-5 pages on a number of minor schools, such as the Sisterhood of the Scythe and the Warriors of White Fire. Each of their descriptions also takes up roughly half a page.
Each description goes a little into the history, where there schools and the like are, notable traits they possess - colors, way they keep their hair, etc, as well as their fighting style. It also mentions favored feats for each group.
Of those, none of the major schools have a prestige class associated with them. For that matter, not even the Sisterhood of the Scythe does. The only schools with associated prestige classes are those that were written up for the Fighters and Barbarians guide.
There's also a number of new feats, but none of them are school-specific only.
So, essentially, the Fighter and Barbarian guide offers up 3-4 more pages on what the Scarred Lands hardcover gave us. There's also a few other tidbits scattered here and there, so it probably ups the page count a little, but there's not much more on them. It does go into other things, though, like mercenaries, barbarian tribes, etc, but when it just comes to the war colleges, there's just a wee bit more info in the book.