I have feared that teaching him ahead would cause more problems/boredom in the classroom so I've limited working with him to looking up particular areas of interest and answering his daily questions.
I'm glad you are going to give Afterschooling a try. I let this fear limit what would have come naturally to me with my son, and it still didn't help, it only made it harder for the school to understand what kind of learner he really is. And it gave him the message that 'academics aren't really that important.' We had him memorizing the lyrics to every Simon and Garfunkle song out of timidity! It took a few years to correct this mistake for us, but I predict it will only take a week or two for you!
And yes, you will have to face that he won't learn anything in school, but he isn't anyway.
Love and More Love,
Grinity