Well, that's literally how children read -- they figure out the sounds from letters and pronounce syllable by syllable, then repeat the whole word (if then don't forget something in the middle of it). Naturally, if there is more than one way to read everything, it kinda doesn't work.
I would expect that to accumulate over years, because less proficiency in early age would mean less exposure to texts of increased difficulty. And if reading is not fun, cool and neither is it easy -- why even do that. Add absence of reading parents and general socioeconomical situation and it makes a disaster.
