I contacted the director of the gifted program at school and received some information. After the teacher referral in the fall he was only tested on the math portion of the Iowa Test of Basic Skills to see if he qualified for the gifted program(ETC in our school). He ranked at the 98th national percentile. Honestly, I was shocked that he ranked that high. While our school scores above average in the state achievement tests, the math scores lag behind the language scores. The school just doesn't have a strong math curriculum. Since the ITBS is an achievement test, I didn't expect him to do as well as he did. He does like to play with numbers, and he's been exposed to higher math at home, so he's been absorbing a lot without any formal plan past the school teaching him how to add double digit numbers.

This is the plan I'm formulating at this time:
1. The one extremely critical thing we have provided him is stability. I think we need to exhaust every option to keep his mind engaged & stimulated, while keeping his friends and his grade placement stable. That's what we have been doing, it just looks like we'll be stepping up the educational activities a notch.
2. His current teacher encourages & welcomes extra activities sent from home. He's allowed to work on his book, work on sudoku puzzles, read as much as he wants for their Accelerated Reading program. I get books from the public library to meet his demand for more books. I'm going to add a few more nonfiction, history & biography books to his selection.
3. I'm ordering Singapore Math books to provide a more orderly approach to his exploration of math at home. He loves doing things like this at home but it's been mostly workbooks I pick up at Kmart to keep him busy for a couple days. His school assigned homework takes less than 5 minutes, only because he writes slowly.
4. He's taking a foreign language enrichment class after school this semester, we'll see where that leads us.
5. We've reached a 'happy place' this year. He's happy and well behaved at school. I enjoy teaching him things which enhance his school education, but I work away from the home/farm and could not homeschool. If you don't have a farm background you may not be aware, but the farm provides a wonderful hands-on, live science labratory, and we turn normal activities into learning experiences. Friday he had first-hand experience with a newborn calf with hypothermia. Not only did he learn about hypothermia(he already knew quite a bit)--he got to save a calf's life. Last year we took a side trip to Gettysburg when we went to a cow show. He knows how to grow his own food, and cook it. I love listening to him practice piano & his flute. We love doing things with his scout den. I love planning projects with him. While building scenery for his model trains we study geology to build realistic mountains, what grows in different climates, etc.

I've read that 'hothoused kids' tend to level off around the 3rd-4th grade, whereas Joe(definitely not hothoused!) started level and has been accelerating at an increasing pace on achievement scores. If this continues to happen, a skip would be more appropriate for Joe in middle school, I think. If he levels off as 'just' a bright student, we'll just have fun doing what we do now.
I'll investigate some additional testing in the next year to have the results in hand should we pursue grade acceleration later. And I'll definitely keep reading here!