Jules, How brave of you to speak up, especially on an Investigations support list <grin>! I am using Investigations for the second year and have had a mixture of success and failure. Our distict uses Silver Burdett as the main math curriculum and Investigations as a support. When the students come to me in 5th grade, they have no background in Investigations, so it's like starting from ground zero each year! I have started the year with Mathematical Thinking, moved into Silver Burdett with Multiplication/Division, moved back into Picturing Polygons, filled in some geometry gaps with Silver Burdett, then back into Name that Portion (really difficult for my kids until they get into using the clock to see adding of fractions), and then I hit decimals in Silver Burdett. I usually end the year with a Polyhedra unit, but may have time to do another Investigation this year that I haven't tried before.
It's what works for me, as the kids really love Investigations and develop a deep love of math. They do not love Silver Burdett, or get much of an understanding there, but they do develop strong calculation skills. I give daily homework (usually calculation practice), and hit Investigations during class time. This keeps the kids accountable to their own work and is something the parents understand too. It's almost like Investigations is the preliminary step into understanding philosophy of what calculation to use and why it works. I also give the periodic assessments that each student must do individually. If they have been taking a free ride, it really shows up here. Failing grade notices sent home to parents wake these 5th graders up real fast! Jacki