23:03
@richard I lean toward start at the bottom, with the important distinction that I don't consider it a barrier to answering any high-level question the student may have. I just consider it the best approach to making a professional who understands in depth what he (or she) is dealing with.
You don't get that level of professional skill in coding camps that "teach 6 languages in 6 weeks" or whatever the claim may be. I have nothing against such programs and they do produce people who can write code. Whether they can easily adapt what they've learned to new languages and tomorrow's architecture may be a different matter.
By analogy: A power plant technician who knows only the exact maintenance techniques in his equipment manuals and doesn't understand electricity or physics, will be unable to adapt when the plant gets all new equipment that works entirely differently. But the technician who understands what he is doing and how it relates to transforming the voltage and modifying the current in other ways, will be able to adapt. The first technician is still employable, but he won't remain so.