If a child does not learn to read, it does not matter how intelligent they are, they are doomed to a life of povety and social exclusion. Labels like dyslexia are almost irrelevent. A child with any IQ level needs to learn to read. I think it would be wrong to give children with low intelligence less than children with high intelligence.
There are certain children who you can tell are at high risk of reading difficulties. For example the children of parents with learning difficulties, the children of those who have no qualifications (especially GCSE English equivalent), those with heaing problems or English as an addtional language.
I think that these children should have one to one attention to help with learning to read from the start of reception. I would go as far to say that they should get substantially extra attention in the early ages before they start school.
It may well be expensive, but if it means children are employable in twenty years time then its worth it.