Some may not know what they want to do but some will. I knew what I wanted to do when I was 10 years old. Your solution is a one size fits all strategy which is what we already have and look at the results. No very promising.
Back in my day we had a some choice. You could start taking vocational classes or take college prep classes in high school. I has no interest in Vocational classes because they were boring to me and most of the skills could be self-taught. I viewed them as a waste of my time and talent. Life is too short to waste time and effort with endeavors that have no value to me.
For my money it's better to provide choices and let the kids decide. Mose of them will figure it out just fine. The rest never will.