I found
this thread about grade skipping after checking into the Iowa Acceleration Scale. (Thanks, Cricket2!) After reading the stories, especially Aiden's, the most like our son, I've come to the conclusion that a grade skip is likely for the best. I could have replaced Aiden's name with our son's when his accomplishments were described at the end of his Kindergarten year.
We'll have our son tested this summer by a psychologist familiar with gifted children and go from there.
We've yet to hear from the charter school. It could be as late as next week.
