The twins are very young to be sent abroad...
Could the school be Institut Le Rosey ? A very posh and expensive school. Marie Chantal of Greece and her sisters all studied there.
https://www.rosey.ch/Exactly one of the schools I was thinking of!

The 2nd school is the one that Chris O'Neil attended.
The Institut auf dem Rosenberg’s boarding students range from age
6 to 18.[6] The Institut auf dem Rosenberg has a staff to student ratio of 1:4 and average class sizes of 8 students per class.[3] 99% of Rosenberg students secure a university placement after graduation.[4] Some 90% of students at the Institut speak 2 languages or more and 60% of the students speak three or more languages.[4] The Institute is one of very few schools offering its students five different paths of education:[2]
