Brain development I would guess too. We are talking 5 year olds. If a 5 year old can read and write well that is pretty advanced. Mathematics comes later. They

Brain development I would guess too. We are talking 5 year olds. If a 5 year old can read and write well that is pretty advanced. Mathematics comes later. They might count on fingers, know some immediate additions, and vaguely understand the concept of multiplication.