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Investigations initially was commercially successful. But parents and math educators have criticized its lack of traditional arithmetic content, of decimal math, of multiplication tables, of division and multiplication of fractions, or even of addition and subtraction of ordinary fractions apart from a small subset, its emphasis on "kindergarten activities" (cutting, folding, taping, etc.) in class and homework, its lack of a traditional textbook; its incompatibility with high-school and international mathematics methods; its non-traditional homework assignments; its high cost (a concern mainly of home-schooling parents); and other factors.
http://en.wikipedia.org/wiki/Investigations_in_Numbers,_Data,_and_Space