I am quickly looking at the history of the Slovenes, and it mentions at the time of Maria Theresa and Joseph II they made compulsorary primary schooling in Slovene, and that a bit later Napoleon put it under a Kingdom of Illyria or something when he got the area. I read somewhere that the Hungarians demanded it be abolished later, though I don't know why. Anyways, providing German education, as well as possibly Slovene, may help tie them down. Or at least to get everyone attached to Styria, Carinthia, and Carniolan identities.
You don’t change language unless it’s beneficial to use in your daily life when interacting with your next door neighbors. You at best Peter your speech with German words and adopt new loan words for new things.