From the inventory:

"The Fradle Pomerantz Freidenreich Collection consists of material collected for use in the preparation of her book Passionate Pioneers: Yiddish Secular Education in North America, 1910-1960 (published by Holmes and Meier, Inc., available January 2010), which covers Yiddish secular schools and summer camps in the United States and Canada and includes over 60 images of letters, memorabilia, and scenes from the schools themselves. This research collection is comprised of correspondence, questionnaires, memorabilia, song books, statistics, articles, conference minutes, camp yearbooks and more, and details the heyday of Yiddish secular schools and summer camps. Roughly half the documents are written in English, the other half in Yiddish. Freidenreich’s own guide to the collection can be found in Box 13, folder 11. Researchers may also find a review of the Table of Contents of Passionate Pioneers useful in working with the collection; click here to view a PDF version.

See also this news item about the book itself.