Purpose: Despite its relevance for the training of a well-rounded physically literate individual, the development of knowledge about physical activity (KPA) is understudied. We examined how KPA is differentiated and evolves according to grade level, gender, and type of school attended by an adolescent. Method: A reliable KPA assessment tool was developed. A three-way analysis of variance was used to analyze z scores on the effects of gender, grade level, and type of school on five different dimensions of knowledge. Results: The reliability was validated. Statistically significant interactions were revealed between grade and school institution on KPA z scores. Main results showed that vocational schools displayed significantly lower levels, compared to traditional ones. The only increase in knowledge according to grade was noticeable only in traditional schools. Results revealed no significant gender differences. Discussion: The French physical education system does not seem to provide an adequate level of KPA, especially in vocational schools.