No sooner did I post my last set of question than someone sent me this study. Note that it is commissioned by the textbook publisher (not exactly impartial research) but one data point nonetheless.
Questions I have after reading this:
--What about other subjects, such as writing or science?
--How does the cost of this curriculum compare to the cost of a regular textbook?
After a yearlong pilot program initiated by publisher Houghton Mifflin Harcourt, students' math scores jump 20 percent compared with classrooms that used traditional paper texts. Read this blog post by Joe Aimonetti on iPad Atlas.