Where are you located?
My understanding from the article I linked to was that, in North Carolina, at least, a DEP was individualized, and was for students who clearly needed differentiated individualized services, sort of like the IEP of gifted services, with the IDP being for children who didn't meet the criteria of needing a DEP.
If your child is in NC and has a DEP, but it is not being followed, or you feel that it is not appropriate, I'd talk to the school about your concerns, possibly after talking more with people from the NCAGT.
