The answer-until-correct (AUC) method of multiple-choice (MC) testing involves test respondents making selections until the keyed answer is identified. Despite attendant benefits that include improved learning, broad student adoption, and facile administration of partial credit, the use of AUC methods for classroom testing has been extremely limited. This study presents scoring properties and item analysis for 26 AUC university course examinations, administered using a commercial scratch-card response system. Here, we show that beyond the traditional pedagogical advantages of AUC, the availability of partial credit adds psychometric advantages by boosting both the mean item discrimination and overall test-score reliability, when compared to tests scored dichotomously upon initial response. Furthermore we also find a strong correlation between students' initial-response successes and the likelihood that they would obtain partial credit when they make incorrect initial responses. Thus, partial credit is being granted based on partial knowledge that remains latent in traditional MC tests. The fact that these advantages are realized in real-life classroom tests may motivate further expansion of the use of AUC MC tests in higher education.