WATER!!! AND MORE...

recently, in science, we got into the water cycle. I find it interesting that here in BC, or maybe just Vancouver, we tend to repeat study subjects, every third/fourth grade, looking at them in depth again. Like, the water cycle is a frequently studied thing in elementary school. Along with greek/roman civilizations, canadian pioneers, etc. It seems that socials/science subjects are taught once in elementary schools and again in secondary school. Is the repetition really neccessary? Is our memory really that bad? Or is there some sort of higher purpose that I'm missing here? Oh well... I suppose that by grade 12, what the government wants you to learn doesn't really matter anymore...