Having good teachers is the key. That is why we need enthusiastic mathematicians to teach math at high school, people with a background in physics to teach physics, etc.
One of the major problem at the high school level is IMO that it is hard to find good teachers connected with all necessary domains. Then, a teacher in 'a branch A' has to teach a 'branch B' that is not his/her own branch of interest... and the worst can happen...