Had the same idea, I own the domain Groupcourse.com built the product and tested it out in a small area. I was profitable but couldn't retain teachers. How did

Had the same idea, I own the domain Groupcourse.com built the product and tested it out in a small area. I was profitable but couldn't retain teachers. How did you solve the retention problem? The experience taught me a lot but now I am repurposing the code for a different product.