 It is also easier for teachers to use since the format is more user friendly, though some districts have failed to carefully implement the second edition as well, and moved back to textbooks that teach traditional arithmetic methods.A systematic review of research into Investigations was conducted by the U.S. Department of Education, Institute of Education Sciences and published as part of the What Works Clearinghouse in February 2013.This found "potentially positive effects" on mathematics achievement, supported by a "medium to large" evidence base.