Go to college even if you major in something dry like, oh, Poly Sci. It is a great place to grow up.
Also take every stage management job you can whether, PSM or ASM. Learn by doing. You can do this in educational settings, community theatre, semi-pro, pro and so on.
Do investigate university programs. But also take plenty of directing classes and psychology ones too. A good stage manager is so much more than someone who manages what happens on the stage.
"If my life weren't funny, it would just be true. And that would be unacceptable."
--Carrie Fisher