It sounds like you've gotten great advice LAF - but I wouldn't give up on the GATE appeal. We're not in CA, but we have a similar situation with our gifted options in public school in elementary where we are (and we also had to appeal - maybe I should say scream? - to get our ds included in the program). It really wasn't anything that ever would have made any kind of difference in terms of actual academics but it made a huge difference in ds' life in that he loved just being with the group of higher ability kids - even though it wasn't a group of EG kiddos. Might not be the same type of situation in CA, but otoh, it might be worth an appeal.
One thing that's also most likely important to look into - getting 504 accommodations for the slow processing if it's impacting him in getting his work completed, both on homework, class assignments, and testing. It's possible that's where he was hit when he took the IQ test if any portion of it was timed (same thing with the OLSAT) - I don't honestly know if those tests have timed portions, but eventually he will run head on into most likely achievement tests that are timed by the time he's in upper elementary if not earlier. Likewise work that may be taking him a little bit longer than his peers now is going to morph into a larger time sink once he hits middle school. It's good to get the accommodations in place now, while you have a relatively recent eval noting the issues.
Best wishes,
polarbear
