If the typical 5th grader is eleven and the average 10th grader is sixteen, it seems absolutely plausible that the gifted eleven year old can do the same work expected of an average sixteen year old at an average school.
IMO, the average 10th grade curriculum would make an excellent 5th grade “honors” curriculum similar to when high school students take average college level courses as honors and AP/IB classes while in high school.
Maybe this is my confusion, I have a hard time thinking in "average" terms.
