From what you say, I highly recommend at least the first few Chalet School books - then if you hate them you can give up. :).

Reading order: http://en.wikipedia.org/wiki/Elinor_Brent-Dyer

(Just for your information, there's a fairly biased depiction of a Prussian girl who they give up on at about book eight), but I think the war books are fairly pacific, although obviously they have the clear anti-German sentiments of anything written at the time.)