Well, since they have just about told you that they are concerned that your son is 2E, I would say it is NOT appropriate for the school psychologist to do the IQ testing. He simply doesn't have the experience with gifted kids and especially 2E kids to be qualified to do that kind of assessment, IMO.
I would want an independent evaluation, if they will accept it.
Also, I get why they are worried about his behavior, but maybe you could get them to just let him "visit" a class for a day or two and see what happens. If he can't handle it for even that amount of time, then there's your answer. But if he does well, then you know that he CAN do well in the environment.
This isn't really an equivalent situation, but my DS was having a hard time in 1st to the point where he was in the office frequently and I was getting the implied ADHD comments "he can't focus or sit still" (although through all of it he was still completing all his work and doing it correctly!) and he was becoming defiant with the teacher, uggh it was terrible. Mid-year they switched him to another classroom after observing that he did better with his math teacher. Once he was moved to her class full-time, all of the negative behaviors stopped immediately. So, changing the classroom environment can make a HUGE difference! IMO, while they may say your ds is just "holding it together" for the 1 hour science class, it sounds to me more like he is actively engaged in a class he finds interesting with other students who likely model more mature behavior, which is exactly what you are looking to put him in during the school day. Even 1 hour is a long time to a kindergartner, so I don't think they should discount his behavior in that class completely.
