The fact that English class is required for all 12 years of someone's schooling says something about the students.
Obviously your logic is horribly flawed. The people that write our newpapers and magazines and novels go to school for 16+ years learning english.

Do I need to know how to find the transversal of a triangle? No, and I forgot as soon as we took the test about stuff like that.
Ok, but someone in your class remembered it, and they are probably using math in their job today. I never liked biology or nature, until I took a biology course in high school because I had to for the diploma requirements. I liked it, and learned that there is so much more to nature than what we see. Now I'm a marine biology scholar at one of the top marine biology schools in the united states. If I wasn't forced to take biology in high school, then I wouldn't be in my position right now.



The best way is to foster a love of learning in your kids, as my parents did, and your child will teach themselves the way the world works and anything else they want to know. All the practical skills that I still use and remember today were taught to myself by myself.
We don't live in a utopia. Believe it or not, every child doesn't have two loving and intellectual parents. And not every child is literate, self structured, and intelligent. Going to school teaches kids structure, discipline, individuality, cooperations, and every other social skill. If you have any friends who were home schooled, then you'd know that those kids lack some major social skills, and in general are very poor at communicating with those who grew up socializing with others 8 hours a day.