Helping students learn only what they don't already know

Well-known, well-validated principles of individual-difference psychology a nd education should lead to major changes in classroom instruction. Student s need to be helped to learn what they do not already know, instead of bein g marched through course materials in lockstep, largely regardless of what they knew at the start of the course. The lockstep method especially hurts the intellectually talented, who tend to be far ahead of grade level. This finding led the Study of Mathematically Precocious Youth (SMPY) at Johns Ho pkins University to devise a Diagnostic Testing followed by Prescribed Inst ruction (DT-PI) procedure. It has been tested often and successfully, espec ially for instruction in middle and high school mathematics, but the proced ure is applicable to other subjects. Nevertheless, the DT-PI model is viewe d by SMPY as merely a stopgap on the road to radical reorganization of inst ruction in schools.