Are you thinking of enrolling him in public school full time, or are you trying to enroll him in a public gifted pull-out but leave him enrolled in the private school?
If you're looking to leave the private school, I would wonder about the same thing ColinsMum mentioned; if you're trying to get him into a part-time pull-out, I might wonder if the teacher doesn't want to deal with having him absent from the classroom once per week (issues like having to make up work missed etc).
I also meant to add to my previous post but forgot - ask if the test is normed against grade or age, because that can make a difference for an accelerated student.
It sounds like the real issue isn't this test though - I think from what you've said the test isn't required by the GATE program, the teacher's recommendation is required. It sounds like you aren't going to convince this teacher to make a recommendation - so I'd move on and talk to a live person who is a part of the selection team at the GATE program.
polarbear
