I am not that surprised that the learning specialist at school blew off the entire idea of him having a subtle reading disability. This is probably more common than not with kids who are compensated (stealth) dyslexics. Without doing the appropriate testing, she would not be able to see the data that supports a compensated dyslexia diagnosis. This testing includes measures of phonological processing, word-level reading skills for novel words (nonsense words, usually), oral (and silent) reading fluency, reading comprehension, spelling, spelling of unknown words (also usually uses nonsense words, and may be called spelling of sounds or grapheme/morpheme knowledge, or some similar term), writing fluency, and spelling/grammar/mechanics in extended writing.
I would not discount dyslexia based on your available data. Some students are amazing at masking their word-level reading disability. In recent years, I evaluated an upper school student who had passed all the benchmarks required, up to that point, and never been raised as one with potential learning issues, although minor behavioral questions had been raised ("attitude", inconsistent work completion). A decade worth of trained teachers thought this student was just your average mildly street-tough kid. Turns out the child had virtually no phonetic decoding skills, and read purely by rote-memorized sight vocabulary. As in, couldn't even consistently sound out CVC (c-a-t) words. By sheer orneriness and determination, this kid had managed to power through classes every year, produce just-adequate writing and reading comprehension, pass state tests--all while literally being unable to decode at a kindergarten level. The behavior was probably mostly a learned response to escape reading/writing tasks that were too difficult (and possibly exasperate teachers into just passing the student along). And this is not the only such child that I have encountered professionally (though one of the more astonishing, for how effective the masking was.)
If a child of essentially average intelligence can fool teachers for that long, it shouldn't be shocking that a 98th %ile kid might be perceived as having no reading issues. It does come with a cost, though, as in my little anecdote. That child has lost the joy of learning that might have been present at the beginning or developed along the way, and has also had to deal with the uncounted subtle discouragements from authority figures, peers, and themselves, who judged behavior as character or motivational defects, rather than as attempts to maintain some pride in the face of serious learning disabilities.
If the school won't test, then I suggest that you go back to the psych and see what resources are available there for further evaluation.
