RTI stands for Response To Intervention, and it's part of the new IDEA (federal special education law). I think it's a good thing, in that its purpose is to catch kids before they fail, and really get more "fixes" in place before it comes to that, but unfortunately the RTI mentality is really only good for kids more in the norm. GT kids rarely "fail" until it's almost too late for appropriate help. The short answer is that without a cognitive/achievement discrepancy entry point (which I believe they can still use....but it's not popular these days), it's hard to identify learning disabilities in highly gifted kids.
Did your evaluation identify learning disabilities? Will that writeup buy you any discussion with the school? Have you pursued a special education evaluation through the school? You have to specifically ask, in writing, to get that ball legally rolling. If you just say "I have this report...", they'll talk you out of it every time. Once it's in writing, it's a more formulated process, that varies from state to state, but is still all covered under the federal umbrella.