My Son Wants To Go To High School!

I've been homeschooling my 15 year old son on and off since 5th grade.  I pulled him out of school and homeschooled him for a year. We met with a homeschool group every week and were having a great time. We was happy learning, and I was having a blast learning or relearning along with him.

 Then, most of the group sent their kids to a brand new charter school that they had formed. My son wanted to go to the new school too because all his friends were going. It was a 40 minute drive from my house, but I did carpool with a friend.  It was a pretty unusual school because it was at least 50% outdoors with much emphasis on sustainability and environment.  My poor kid has allergies, and suffered through the school year. Plus, they ate lunch outside and he won't eat outside because of bugs, so he always waited til he got home to eat.

 Then, he homeschooled the next year since the charter school didn't work out. (there were other issues with the charter school too)

 The next year we moved, and he wanted to try 7th grade in the new school system.  That lasted a couple months, then we went back to homeschool.

NOW, he is 15 and is afraid that he'll regret never going to high school. He wants to try it out and see what it's like. I don't blame him for that, I guess. I don't want him to have regrets later.  Of course, they will put him into 9th grade. (I'm assuming, anyway) He is 6'1, weighs 240 lbs (is trying desperately to lose weight, and making some progress) and everyone thinks he looks 18.  He's gonna stick out like a sore thumb.  Those highschoolers  are gonna eat him alive.  I don't want him  to go, but as I said, I don't blame him for wanting to try it.  I wouldn't want him to blame me for any regrets later on.   Plus, he just decided this 2 weeks before school starts.  Ugh!