MegMeg,
I know where you are. For the last few weeks, DD has been asking to be homeschooled for K. To make a long story short, I'm leaning towards sending her to a full-time K mostly because I cannot imagine being organized enough to do it right.
But, If I were to homeschool DD, I'd be open to taking another child. DD would be thrilled to have an older sibling figure so I'd be looking for a child who is a couple of years older. We'd be unschooling although after age 8, there would be some expectations for writing and math fluency.
I would not charge what I'd charge as a tutor as I see it being beneficial to my own child and I'd want it to work financially for both families.
If you put words out there that you are looking for a HS partner family, you might find someone who is willing to customize your DD's education based on your vision and DD's developmental needs.
