Educational technology is compelling, largely because of its promising capability in enabling differentiated instruction. In a classroom of 30 students with diverse abilities, technology can allow teachers to more effectively instruct students within this wide range. However, the promise of using technology for differentiation relies on a range of high-quality information used to (1) diagnose students' learning needs, (2) map those learning needs onto the program's objectives, and (3) evaluate the evidence for the program. [This paper was published in "ASCD Express" v9 n18 Jun 2014.]