The lexile score is a completely different test than the OLSAT so he was presumably given both. I didn't think that the OLSAT was sensitive enough to go beyond the 99th to the type of scores your ds got. Dottie kind of covered that one already anyway, but it certainly sounds like he would test well on an individual test. His school is likely to id him as gifted without the individual testing, though.
I'd go with individual testing if you think that he would qualify for a program like Davidson Young Scholars or if the options available with a GT label in school aren't sufficient and you need ammo to advocate for more.
As far as the lexile, it is a reading comprehension measure. His score puts his reading on par with early 5th grade.
http://www.dupage88.net/aths/resources/AT%20MCweb02/TEAMS/ELLResources/LexileConversionChart.pdfHonestly, that doesn't tell you as much as the OLSAT, though. My dd12 had a lexile above 1000 at that age and she is not profoundly gifted. She's just an excellent reader. There are likely some PG kids who didn't read as well early b/c that wasn't their focus or strength area. It is still a very strong reading score for his age.
