There is the decoding (the ability to say a word that is written) and the understanding. Decoding is easier for most children, and they can decode sooner most words before they have understanding of those words.
So, teaching a child to read may not be as important as just reading to them. Reading to them allows them to build up a larger vocabulary, and allows them to give meaning to decoded words.
Putting this in the context of parent volunteers in schools: it's easy to see that a parent may be pronouncing the phonic sounds incorrectly, or may be subverting the techniques (moving to a look and say technique), or just generally adding some sub-optimal hints and shades.
I don't know about the HN population but methods for math have changed quite a lot. I'm re-learning so that I can help my son. There are very many innovations.