> In 7th grade, in the fall you are taught X, so if you miss it the only solution is to take it next time

In my experience in elementary school, 3rd grade material is repeated ad nauseum in 4th, 5th, 6th, 7th and 8th grade. Plenty of time to get it. (Being an Air Force brat, I attended 3 different elementary schools, even one in Germany run by the military. All the same.)