I don't think there are really any "typical" grade skipping policies. It seems rare in most places, but in our local district there was no policy when we asked for one. We did give the school the Iowa Acceleration Scales, and they now use that as part of their policy. Have you checked the district web site for policies?
That said, we did what you mention above. We had our January birthday son go to kindergarten with agemates, mostly because he was not used to full-day, every day school and also because he refused to learn to write at home and that's one thing he could learn in kindergarten. The school was also supportive (eventually) of differentiation for DS. Then we skipped 1st. This worked out fairly well, but even with the grade skip and differentiation, pace in the regular classroom was an issue. (We then found an accelerated program and transferred DS.) We probably could have stayed in the local district, which by then knew what DS was capable of and was willing to be fairly flexible, but it would have required yet another grade skip, which we didn't want. At least not yet.
It may be a good idea to approach the school with your 2 ideas and ask for their advice. They may be willing to test your child, on their own tests (which is more convincing to them).
