Thank you to Joe Merlino of The Greater Philadelphia Secondary Mathematics Project for calling our attention to this report. It is the final report of a 4-year longitudinal NSF research study investigating the mathematics learning at a suburban high school that had adopted both a block schedule and the Interactive Mathematics Program (IMP) curriculum. The study compared the combination of the block scheduling and the use of this integrated NSF funded mathematics curriculum to a traditional schedule and traditional math curriculum at the same high school. In contrast to previous research that showed a decline in math achievement at schools that adopted block scheduling without changes to math curriculum, the combination of these two reforms did produce improvements in student achievement.
To see this paper in its entirety, you can use this link: http://www.gphillymath.org/BlockSchedule/