I think there may be separate questions. One is how to determine access to a program or a course, and the other is the content of of the program or the course.
I think these questions are intimately related. You can't know how to identify students who would benefit from the program before you have determined what that program is. I highly recommend the book
Beyond Gifted Education for anyone considering these issues.
Also, regarding Val's comments about open access to gifted programming, I've read about a district (or it might have been a school) in Hawaii that did this and it was a huge success. Unfortunately, I can't find the source right now. Anyway, the key was, like Val said, not lowering the standard of instruction. If I come across the source, I will pass it along.
