In early 1860 the nation of the Union of Soveit Republics (USR- Yeah Communism was a thing much earlier in TIO Mundus) invaded Kaitaine in order to gain access to ports. In the midst of a shortage of food and with the nation run by its religious Bene Gesserit leader, known as the Reverened Mother (Think Pope but cooler outfits and crossed with an autocractic monarch) who was not a good leader the nation fell under USR rule very easily. The Bene Gesserit leadership replaced the Reverned Mother and packed its significant bloodlines (need to breed the superhuman) into hiding. They picked four countries that they felt would be suitble.
1. Ui Cenneslaig, ethnically the Kaitainites are Celts and UC is the Celtic homeland of sorts.
2. Achkaerin, continental neighbours and rather liberal in outlook.
3. Cantabria - another celtic nation
4.TBC - Some reason we agree upon.
By the early 1870's the Bene Gesserit had established small outposts and the faiths paramilitary arm known as the Truthsayers were busy trying to sneak more and more out. By 1880's the schools had been established. Periodically the Bene Gesserit have attempted to retake their homeland, usually failing miserably.
The COmmunist government of Kaitaine was a puppet of the USR until around 2014 when the USR collapsed leaving Kaitaine as the global HQ of Communism. In the 1920's the government of Kaitaine banned all religion in order to try and end the Bene Gesserit uprisings but this hasn't really succeeded. In secret the schools and those loyalists still in Kaitaine have seen fit to keep fighting as and when they can.
In 2016 the Kaitaine Guard Buereu (KGB - Kaitaine's Secret Service) discovered the identities of Bene Gesserit leaders across Mundus and began assassination attempts as well as undermining the security of the schools, effectively blowing their cover as just selective girls boarding schools. Upon the discovery of the schools the Bene Gesserit were welcomed in UC and Cantabria, Achkaerin too recognised them as a legitimate faith. In 2017 rouge members of the faith tried to steal nuclear waste from East Moreland who declared the faith a terrorist organisation, as too did Rokkenjima.
In 2018 the Bene Gesserit launched a surprise uprising in the West of Kaitaine and successfully took back their most holy city, Seitch, from the Communists. They soon after declared the nation to be the Free Theocracy of Kaitaine with Reverned Mother Erin McGregor (who is based in Ui Cenneslaig) as Head of State. ICly I believe only Tamora have recognised the Theocracy as legitimate. There is currently a civil war going on in Kaitaine between the Bene Gesserit and the Communists.
So this school will have been in place since the 1880's, be respected for its academic excellence and be full of highly religious Celtic girls
If you have any specific questions feel free to ask.