FACTS - Section 504 requires that schools identify students with disabilities and remove any barriers to accessing the general ed curriculum. There is no requirement to maximize student performance. It is to "level the playing field" as opposed to giving any advantage and should never change what a student learns, which would be a modification.
On the other hand, accommodations are allowable in accelerated classes if they are based on the student's needs in the general education classroom. In other words, accommodations necessary in the general education classroom should generally be provided in the accelerated classroom unless the accommodation fundamentally or substantially modifies the program or its standards.
A student who wants additional accommodations (beyond those he/she currently receives) in order to tackle the more difficult subject matter, speed, or coverage of the accelerated course would appear to have no entitlement to the expansion of the service plan based on the move to an accelerated class. Therefore, the district has no obligation to provide them.
Under the ADA and Section 504, "an educational institution is not required to make fundamental or substantial modifications to its programs or standards."