MP, there is not a lot more the teachers can do to make the request more effective, if 100% extended time is already listed as that in your IEP accommodations, and they've already looked at your evaluation scores. In my experience, the College Board is usually looking for a processing speed score below average, and some academic fluency score below average (such as reading fluency or math fluency). I'm assuming here that your teachers are already using the guidelines provided by the CB for extended time documentation:
https://www.collegeboard.org/students-with-disabilities/typical-accommodations/timeYou may also being dealing with the fallout from past abuse of the accommodations system. The CB appears to be really cracking down on extended time 100% (which requires school-based testing, not center-based testing).
I would encourage you, though, to take a more optimistic view of your capacity to demonstrate your skills effectively with time-and-a-half. I don't doubt that 100% extended time is appropriate for you, but it doesn't necessarily follow that 50% extended time will be catastrophic. In the event that you are not able to get the accommodation for AP and SAT exams, you will still be able to do quite a bit, and it very well may be enough. It may involve a bit more test prep (since practice is the friend of fluency and speed), but you are still a bright and capable person, even when you don't have 100% extended time, and, as sanne said, there are strategies you can practice and apply to help a bit when you don't have full access to your accommodations.
Many colleges are definitely moving toward test-optional, including some very big names, so don't feel like test scores that aren't fully reflective of your skills will keep you from a good college education. Also, many state universities will take your neuropsych evaluation in place of the SAT reasoning tests (not the subject tests, of course). Many colleges also allow for taking a local placement test to test out of entry level courses. They may be more open to accommodations through Student/Disability Services at that institution. I just want to reassure you that there are multiple pathways to reach your college goals.
