Jenafur-
Early entrance is one option that seems to work out very well for gifted kids. They don't have the stress/stigma of a grade skip that peers are liable to be asking about, and a mature four year old can blend easily with a group of 5 year olds. I think it is definitely worth pursuing, though the reception you get will vary wildly depending upon your state policy and the particular school you approach.
For kids who are HG+, many times two grade advancement is desirable. This may be achieved by combining early entrance with a later skip, two single year skips in different years, or a more "radical" two year skip. I encourage you to read the Templeton report (A Nation Deceived) for details on acceleration studies.
http://www.nationdeceived.org/Homeschooling is another way to accommodate gifted learners who are more than a bit ahead. It's been a great blessing for my family, where the kids are all profoundly gifted but also have 2e challenges. I'm pretty sure that my one undiagnosed kid is also going to meet the criteria for ADHD. She is very active, and I can see a lot of parallels to her sister who is ADHD. She's unmedicated so far, which we'd probably not be able to do if she enrolled in school. Not many teachers want their pupils bouncing around while they do their lessons.
Good luck!
