We let parents decide when they are homeschooled, but we are very clear they don't get to flip flop. They either choose by age or by grade in this situation, but say next year he has a friend in the lower grade he doesn't get to then decide to say he is in the a different grade because of his age, he will always be with this 3rd grade group of kids. Also, our policy is that older kids can move down in grades but younger kids can not move up, so in this instance, if it is anxiety, the sister could go to 2nd grade with him. Most parents don't like kids moving down, so it usually prevents a lot of issues.