The more I work with kids who struggle, the more I think the big culprits are: 1. Developmentally inappropriate expectations beginning in kindergarten 2. Failing to teach handwriting to mastery in k-3 3. Failing to use evidence-based instruction in reading and mathematics. Some of this may be classified as "dysteachia" but you cannot teach what you do not know -- our teacher preparation programs are deeply at fault.
I got a 504 for one of my child because 1. she is bright 2. she can't handle the endless repetition in mixed ability classroom 3. She will cause trouble if she has no work to do in class. I would have gotten a 504 for my older child if I had known about them early enough. I have an IEP for my youngest. They likely have no learning disabilities aside from dysteachia. However, the only tools I had to use to get appropriate schooling was a 504/IEP. When all you have is a hammer, everything becomes a nail. If I could have gotten my kids into a homogenous class, I/they woud not have needed a diagnosis.