I learned CAD, HTML, C++ and numerous other computer skills in middle school and high school. Some of them were elective classes, but the basics were introduced in basic computer courses. If you liked an aspect of a certain computer code, you could then take a more advanced class for the elective.Kids need more then just typing skills now though, excel, programming, and other computer skills are needed a lot more. That being said most teachers still teach it just depends on how up to time the kids are with all their subjects, if they need more time with different areas it gets cut from that particular class, or at least thats how i understand it
Maybe my school system just offered us more independence in what we wanted to learn outside of math, science, history, literature, and phys ed? Heck, my junior year of high school I was taking both Physics and AP Chemistry, in addition to CAD classes and even a journalism class. In fact, I had to get permission from my Journalism teacher to miss class once a week for one of my science labs (and missed gym once a week for the other lab).
Schools can fit anything in if they're creative enough and get the parents' blessings.