“Wisdom is brought about by need. I think there’s a need,” said billionaire tech entrepreneur John Marshall. Marshall is among a growing group of ultra-wealthy founders who, in recent years, have taken on a new role in South Florida: private school creators. Marshall moved to Miami Beach in 2014 and later became a father of two daughters. When one turned 4, he began rethinking traditional education. “The more we peeled back what we wanted in a s…