Val, St. Pauli Girl, and polarbear, thank you all so much! I really appreciate the responses.
In this district, GATE identification is done by OLSAT (I think 90-95% cutoff) for most part plus teacher recommendations. I think portfolio review can come in for older kids. DS's home school is one of the top schools in the district and has high API scores and a good deal of extras due to the deep-pocketed families in area. But after having numerous conversations with the principal and the GATE teacher liaison, it is abundantly clear that GATE ed is a low priority at the school. I was even fed the line that the school wants the GATE kids to "inspire the low performers". Hence, the anti-clustering policy.
Probably the biggest problem I am having with the current home school is the classes are fairly crowded and, according to the teachers, populated with an abnormally high number of "misbehaving" kids. Who knows?
The magnet school is open to the district. There is an all-GATE class for grades 1-5 at the school and the rest are "fundamental" classes. All hopefuls (GT or not) go into the lottery and are selected. The lists are kept by grade and then by GT/non-GT. There is often more room in the GT classes but not always. The parents I've talked to have loved it but I don't know any from my homeschool who've gone that route.
Val-yes the student body in the non-GT classes would not be much different from other schools.
I just thought of another question for you all. When viewing the GT classes, what types of student/teacher behavior should I be looking for (other than the complete opposite of what he has now in class)?
Thank you all again so much! It is so helpful to have this resource.