This article, by linguists Joe Salmons, Chris Tabisz, and Mike Putnam, talks about German heritage speakers in the US.  Among other things, it talks about the history of schooling in German:

“Taking the German School of Madison as an example, the core of the school community consists mostly of families who are either ex-patriots from a German-speaking country or mixed families (typically one German parent and one American parent). Many of those families are connected to the University of Wisconsin – Madison and therefore come and go depending on their employment in the United States. With the growth of the school, more monolingual English-speaking families have begun enrolling their children. Many of these families have heritage connections to the German language, for instance German-speaking ancestors who lived in Wisconsin, and such monolingual English-speaking families often still identify with German heritage. There is a gap between heritage speakers and their grandchildren or great-grandchildren who are now interested in reconnecting with their ancestors and their cultural heritage by learning German as a second language, but the motivation and enthusiasm for the education of German language and culture appears to be increasing today.