Not snarky but, as opposed to what? No school? An arts degree? Or are you looking for an alternative to an undergrad biz school degree that's more start up focused?
Plenty of school now seem to have entrepreneurial programs. Maybe a undergrad school that has an entrepreneurial emphasis is your best bet?
I think it depends on where you want to fit in a start up? For example, if you want to do customer acquisition then marketing (and analytics) which is more biz school than STEM might work. Product dev, same. But if you lean to something more technical then go more STEM-y.
Plenty of school now seem to have entrepreneurial programs. Maybe a undergrad school that has an entrepreneurial emphasis is your best bet?