Start on the district web page, look under "student services" or "special education" or something along those lines.
I've only heard the 23 point split as qualification criteria verbally (both to me and to at least two other sets of parents I've spoken to) in IEP-qualification meetings. I've not seen it written down, and I suspect that this is because they don't want to have to live by this as a hard and fast rule.
In all cases I'm aware of in our district, both the parents and the teachers also had ample additional evidence that it was affecting the child's academic progress or social/emotional state. In our case, that's too bad, because the phonemic awareness problems were evident long before then, and now we have to do both intervention as well as emotional repair work.
