The testing effect is the enhanced retention of learned information by individuals who have studied and completed a test over the material relative to individuals who have only studied the material. Although numerous laboratory studies and simulated classroom studies have provided evidence of the testing effect, data from a natural class setting with motivated students are scant. The present two-class quasi-experiment explored the external validity of the testing effect in the Introductory Psychology classroom. The control class studied assigned chapters from the textbook whereas the quiz class studied chapters and completed daily quizzes on those readings. Subsequently, both classes completed exams over this textbook information. The quiz class scored significantly higher than the control class on these test questions about the textbook information; these differences were significant both when the test questions were the same as the quiz questions and when they were new, related questions from the textbook. These data suggest the use of daily quizzes to embed the testing effect into the Introductory Psychology classroom can improve student learning.