I disagree. Calculus should be taught in primary school. Otherwise, they are not going to get to the standard model by high school :PI don't think that you can use the Feynman Lectures in highschool. They are full-fledged introductory physics books at the university level, and I'd say they are rather theory than experimental books.
Nevertheless I agree with you that physics in the final classes of highschool should be taught calculus based, and I consider calculus a mandatory subject for any high-school student. Calculus must be consider a topic of general education for anybody at a high school, and indeed applications in physics are very nice examples for its applicability in real-world problems. In fact math is the key to almost everything in the modern world from the natural sciences and technology, including informatics to economy, sociology etc.
In other words any didactics, which tries to "avoid mathematics" in any STEM subject is flawed to begin with.
OK, I concede that's a bit much. QED would be enough, but they must be taught the proper Wilsonian viewpoint.