In January 2006 the Billings (Montana) Public Schools adopted a computer-assisted instruction (CAI) intervention aimed at helping students recover credits that they had attempted but had not attained. The author volunteered to teach the algebra component in his high school. Through the following seven semesters, he came to better understand the role of an effective teacher in a credit-recovery program that relies so heavily on CAI. This article is an effort to describe this effectiveness and the nature of success and failure in CAI interventions.