My son recently tested into the program at Northwestern and took his first two classes. He just turned 7. They have little kids in the program and it is really cool. We live a few hours away but travel there for him to participate. I'm not sure how the online classes would work for such a young kid. We haven't done the online classes yet although we intend to.
FWIW e also pulled our son out of first grade to homeschool him. He is doing much better at home.