Welcome to the board. Here's my 2 cents.
1. His current school is quite rigid in the sequence of work and the repetition required, which is causing boredom for DS. Maybe testing would convince them to be a little more flexible?
In my experience scores have helped a bit but not as much as I would have hoped. Some schools/teachers get it, some don't. Wherever they are they can be swayed slightly but generally not from one extreme to another.
2. We would have more time to review options before deciding on a school for first grade. Taking the WISC next March, around the time we should be committing to a school, may be rushing things.
Not sure where you live (feel free to PM if you want to know where I am) but in our city for public schools even June would be ok. Private schools are a whole other ball game though.
3. It may give me some peace of mind to have a better idea of what we are dealing with. I am confident that DS is gifted, but I don't know whether his level of giftedness is going to require major accommodations.
Totally agree on this one but I will add that personality also plays a part. My kids both dealt with school in very different ways and IQ scores weren't the only explanation for that.
4. DS is starting to become very self-critical about minor things. Maybe testing would give us some insight on how to support him emotionally.
Assume he is and go from there. Parents are pretty good at guessing this stuff.
1. Waiting a year might give us more accurate/stable results.
Yes - we tested at 6.5 and weren't able to get accurate results at that time with DS. We had to then test again 2 years later.
2. I've heard that ceiling issues might cause problems for gifted 5 year olds taking the WISC.
I'll leave this to the testing experts...
3. If we also do achievement testing, more current tests could be used to help his new school give instruction appropriately matched to his academic level
We didn't even bother with achievement testing for DD because we knew it wouldn't change things with the school. IQ scores were enough to access what we needed to access and teachers would either do something or ignore them so we saved the money.
In general I think it is important to understand more info about what the school you are looking at will accept for tests and their timeline. One of the school boards that my kids is in will only accept WISC scores for example (although to be fair they don't have a congregated program that 5 year olds need qualifying scores for).
