Many teachers believe that denying students the opportunity to retake tests and redo assignments teaches them responsibility and prepares them for the working world. In reality, writes Wormeli, this practice has the opposite effect--it retards student achievement and maturation. In the real world, adults learn by repeated practice; they are not judged during the learning process, but only when it's time to demonstrate final proficiency or become fully certified. The logistical challenges of implementing a redo policy should not blind teachers to the importance of requiring that students master content instead of simply receiving a low grade and moving on, writes Wormeli. An experienced teacher, he offers 14 practical guidelines for managing redos in the classroom. (Contains 1 endnote.)