That's pretty specific to Pathfinder, and may not be useful in keeping the extension usable across multiple rule sets.
On the other hand, if a Pathfinder-specific extension is desired, I'd probably advocate for something like the NPC sheets, where choosing the type (NPC or Trap/Haunt) makes specific combinations of fields available. The schools are an adjunct to the Factions of the Faction Guide, and the fields are different.
Affiliations in 3.5 were different enough that I am not sure one extension could serve both Affiliations and Factions without having several unused fields depending upon whether you were using Affiliations or Factions. A few fields would be generic enough to be common, of course.

