In this article the issues of validity and reliability in the assessment of the learning outcomes of WIL curricula are considered. An argument is made that there are three classes of learning outcome for WIL curricula: experience of the work-world; the development or refinement of skills; and the application of disciplinary knowledge in work contexts. It is noted that the protocols for assessing the first two of these outcome classes have a longer history and are better developed, in terms of established validity and reliability, than those for assessing the third outcome class. An elaboration is then made of the scope and meaning this third class of outcome, and it is argued that the naïve notion of "application" can be developed fruitfully in terms of three requirements that force the explicit integration of theory and practice: (1) interpretations of the setting; (2) predictions about the impacts of possible future action scenarios therein; and (3) action choices. When all three are justified by reference to disciplinary canonical knowledge and theory a strong case can be made that students have successfully integrated theory and practice. This idea is developed and a generic rubric is proffered that may be of use to WIL curriculum designers and assessors.