Arguably there's no school for any high position of leadership. That said, Theodore Roosevelt was remarkably well prepared for the presidency. He had held executive positions in the military, in local government, in the federal government.
President-elect John F.Kennedy said to Robert McNamara that there's no school for presidents, or, for that matter, for secretaries of defense.
I attended law school, the progression into a career in corporate law was almost foreordained. I set about to craft a career reflective of my values. These included: public service, environmental protection, and leadership development. Trusting my instincts, following my heart, enabled me to create a calling that became a career.