Respectfully suggest that speed reading is a separate issue. Typically, it’s something that grown-ups do after they can already read.
This article deals entirely with how reading is taught when a child is age 4 to 7, let’s say. Elementary school. These days almost all children in the US are given lists of sight words to memorize, such as you’ll see here.
Memorizing so many sight-words with automaticity is almost impossible for most children, so they remain in a state of semi-literacy.
It's interesting that voice and text recognition systems break sound and print into phonemes. So a computer "learns" to comprehend and "read" using those building blocks. If they're good enough for a machine, why aren't they good enough for our children?