To measure the procedural and conceptual knowledge of functions and to clarify the relationship between them in the context of mathematics education in Morocco, a structural equation modeling (SEM) analysis was used. In addition, correlation tests between students' grades at their Mathematical Analysis Assessments and their procedural and conceptual knowledge of functions scores were established to investigate whether students' grades mainly reflect their performance on procedural knowledge or conceptual knowledge. The sample consisted of 337 high school Moroccan students. The study findings indicated that a large group of participants scored high in procedural tasks but low in conceptual tasks. Besides, the participants' grades in their exams correlate much more strongly with the estimated procedural knowledge scores than the estimated conceptual knowledge scores. On the other hand, the confirmatory factor analysis of the SEM confirmed the reliability, validity, and fitness of the measurement model, whereas the path analysis of the SEM supports the genetic view causal relationship that procedural knowledge of functions is necessary but not sufficient condition for conceptual knowledge. These results provide a theoretical foundation for improving mathematics education by working on the content of the assessments, the teachers' teaching approaches, and the students' learning strategies.