JumpMath (www.jumpmath.org) used largely in Canada believes in introducing fractions before moving further along in multiplication/division. They claim they have data showing the importance of introducing fractions (including adding/subtraction fractions with different denominators) at this early stage, so that kids can have a better foundation early on in math. I was tempted to have my DS follow their curriculum. He could understand how to add/subtract one third to one forth. But, since his school doesn't introduce fractions until after long division and averages and EPGY doesn't introduce them until later, it was too much work to do myself.