This is quite a relevant issue for me because I have taught computer programming to primary school students in New Zealand. Teachers need to not only be taught how to program themselves but also how people learn programming. Which concepts are contingent on the understanding of other concepts.
Every programming teacher (myself included) that I have encountered is just someone who knows how to program muddling though best that they can.
I attended a seminar on how numeracy is taught in NZ. They have a lot of information about the order and time it takes for individual concepts to be grasped. Information from similar research on how children learn to program needs to be coalesced into a teaching plan, and teachers need to be taught that plan.
Doing this right will be a tough job. It will require resources. Probably more resources than will be provided.