I don't have any advice - but I do recall very clearly hating one of the accommodations I had in my IEPs from elementary through middle school - school district dropped it when the cost vs benefit was not worth it (the teachers kept accidentally destroying the system or forgetting it, and I had made it clear by middle school that I did not want it anymore), but in return, I agreed to other accommodations to make up for that including extra help in resource rooms as needed during scheduled periods.
I would agree with DeeDee on asking him to have some alternatives that the teachers may support. Like one example maybe - on test days, could he go in earlier to do the test that includes the extra time, and then do assignments while the class is taking their test in the school day or something like that? I had that for oral exams, where I met with the teacher outside of class time (before school, after school or during a shared free period) within the same day or next day (oddly, I don't recall what I did while the rest of the class did their oral exams but no one blinked or said anything that I noticed).
