Is your math curriculum coherant?

Is your math curriculum coherent?

You probably know that in international comparisons, US students don't do real well in math. According to TIMSS studies, US fourth graders are just above average, eighth graders are just below average, and twelfth graders are well below average.
There are many reasons for this. William Schmidt, Richard Houang, and Leland Cogan have done research into the curricula in the best performing countries versus US, giving us one clue as to why it happens. The following article of mine is based on their report A Coherent Curriculum: The Case of Mathematics, which appeared in Summer 2002 in American Educator.
Schmidth et al. compared the national curricula of the best performing countries versus US state standards and district standards for math (since US does not have a national curriculum). Several differences emerged:

US math curricula tend to be
not focused. No country in the world covers as many topics as US in their mathematics textbooks. For example, in Japan, eighth-grade textbooks have about 10 topics whereas US books have over 30 topics.
highly repetitive. The average duration of a topic in US is almost 6 years (!) versus about 3 years in the best-performing countries. Lots of spiraling and reviewing is done. Like Schmidt says, "We introduce topics early and then repeat them year after year. To make matters worse, very little depth is added each time the topic is addressed because each year we devote much of the time to reviewing the topic."
not very demanding by international standards, especially in the middle-school. In the USA, students keep studying basic arithmetic till 7th and 8th grade, whereas other countries change to beginning concepts in algebra and geometry.
incoherent. The math books are like a collection of arbitrary topics. Like Schmidt et al. say, "...in the United States, mathematics standards are long laundry lists of seemingly un- related, separate topics."

(http://www.homeschoolmath.net/teaching/coherent-curriculum.php)