Teaching elementary versus teaching secondary is like teaching a kid to ride a bike for the first time (training wheels and all) versus teaching a kid how to ride a dirt bike. It's just a different world. With primary education, you're teaching them everything. Literally. You're teaching them how to read. You're teaching them how to count, how to add, what a sentence is, what a noun is. You are teaching things completely new and unknown in their universe. You walk through every step with every child. With secondary, you are expounding upon the basic knowledge. The kids already know how to read and write and add/subract. Now teach them to multiply, teach them algebra, teach them physics and biology, teach them US history. The kids already know the foundations for everything you're about to teach; it's just hoping they're motivated enough to do it and won't make your life a living hell.