Highly recommend YC startup school. Latchel went through startup school during the infancy of our product. The accountability and direction put us on track to predictably drive sales every week. I'm 100% certain that the startup school experience is also what got us into YC's W19 batch. Lots of parallels shared between startup school's structure and YC itself.

Even if you don't intend to apply to YC, you'll be able to apply startup school's concepts to help grow your business.