I am a bit surprised at the uproar. A short intervall spent abroad isn't something so very out of the ordinary in my circles, so I can't find it so overly disruptive for the children. I know many children who spend some months, weeks in France, Britain or the US to give their language skills a bit of a boost and/or to help them with their social skills.
German friends of mine eg. have just send their daughter to Carlifornia for a 2 months trip - enough time to help with english, not enough to get her out of her current school-plan.
I think it's that this isn't/hasn't been done in the DRF before; it would be "normal" to send one or two children off for a bit of polish but going from "zero kids/no tradition of sending any kids" to "all four are being shipped out".
I also come from a background where it's normal for a child/teenager/collegiate to spend some time abroad, even over a year depending on how deeply immersed they become (or if it's a three to four year program).
This is not the norm for this family; thus it raises eyebrows. (I'd have recommended a cloistered convent for Josie, preferably a silent order, but that's just me).