Age 11, began Harvard University's Extension Program he graduated at 16.

[dfrecore]

I second the opinions of dfrecore and Life Long Learning, especially regarding socialization. Saying that kids who don't go to school with kids their age don't have friends is simply factually incorrect, any way you slice it. I split time between being public schooled and homeschooled, and every one of the friends I stay in touch with is from the "homeschooled" times. Kids learn to socialize in the real world much better by actually socializing in the real world than by being put into an age-controlled environment.

And you can't possibly know what the kid can or can't grasp. There is a normal expectation for what kids can grasp at what age, but there are many exceptions. For example, when I was in 2nd grade my dad was doing his student teaching to teach high school history. As an experiment, my parents had me do the assignments from his 12th grade U.S. History class and graded them on the same rubric. I was one of only 2 or 3 students to get an A in the class.

And let's not forget, this kid DID go to school with kids his own age.  He was enrolled in high school and spent 8 hours a day there.