This is really not an answer to your question - just an elaborate comment, and opinion based rather than factual. I hope I will be forgiven...
The idea of breaking "science" into disciplines at an early age goes counter to the way exploration by young minds ought to work, in my mind. When I, as a four year old, was playing with a magnifying glass to burn bits of paper and occasionally ants, was I doing physics, chemistry, or biology? Answer - I was doing none of these. I was doing
"natural science", exploring the world around me. Similarly, when I constructed an incubator for chicken eggs - was that biology, engineering, physics, environmental science? Exploration and curiousity knows no boundaries - and that exploration is what builds excitement and forms minds that can synthesize concepts to create breakthrough ideas. Instilling that "random walk through the natural world" approach can build intuition, and should come before the formalization of science into disciplines.
Interestingly, when I went to study physics in the university, there was no such course. We started in what was called "Natural Sciences" (even at that level) and took courses in a number of different branches before "majoring" in one field.
One final thought: don't blame it on "the bureaucrats". Amazing teachers always find a way, although that leaves progress only on the level of one class at a time - to make progress with an entire education system you need changes that go well beyond the bureaucracy. Small plug: "The smartest kids in the world, and how they got that way" . It's a book I recently saw in a store; I admit to picking it up and browsing only, but I think if you're interested in the future of education it will provide food for thought.
As I said: not really an answer. This whole Q&A probably belongs on a different SE site...