Hello again!
In addition to the private math tutor, I'm also interested in Keystone Online High School. Any experience with this? I think it might require some supplementation in order to keep ds well-read and moving forward with math, but it would give me a "spine" to work off of, and would give him the opportunity to earn tranferrable credits. They do not care about the age of the child, as long as he can show evidence of completing eighth grade equivalent work (test scores count). Also, they will review his homeschool transcript, and he can potentially transfer in credits for the high school level courses he has already completed at home.
In our area, there is a special free university-run math and science academy for gifted 11th and 12th graders. If he could earn enough credits through Keystone to become an official junior, he may have a good chance of being accepted.
Hello Kitty, (that sounds funny)
It seems like you already had an answer. Sounds like a really good plan. You should apply DYS just in case your DS may want to do summer camp there. They do give out scholarship.
Good luck!