Ed, (that will be easier than mcsquared)
My DD8 (4th grader) skipped K.
During 1st grade, there are many high achieving kids and she is one of many high performers. By 2nd grade, she is clearly top of the class. We moved to a new school this year. They have TAG classes that teaches 5th grade level. (She could do 6th-7th grade level Math and LA but she has some gaps) There are a few kids who were better than her at the start of the school year but it seems like she caught up with them already. It's just a matter of time that she would become the top cat (she likes cat nor dog).
HG and PG usually needs 2 or more grade acceleration (granted with no 2E issue).
Your DS will be fine after grade acceleration. He probably will need more later on.
