This commentary points to several measurement issues that arise in assessing medical student performance outcomes and then discusses the challenge of interpreting between-school differences. A problem often encountered in assessing student learning is creating an instrument that is at the right “pay grade.” If it is too easy, ceiling effects compress scores. If it is too difficult, examinee performance can compress about chance values, and morale problems can occur. These issues are discussed in the context of a report by Williams and colleagues that measures medical student performance across five institutions on instruments assessing diagnostic pattern recognition and clinical data interpretation. The author of this commentary observes that, when interpreting between-school differences in assessing student learning, what can seem like small differences can have important consequences.