While I understand the concept of fluency, and agree that it is important, certain kids are not fast and never will be. Faster does not mean smarter.
If your child were diagnosed with a learning disability, you could get accommodations for this. But slow processing on its own is not usually considered a disability, so there is little "legal" footing for your argument. (not that the law helps in all circumstances!) I agree with Val that accuracy is more important than speed.
Drea45345 mentions motor issues - sometimes a low PSI is in part due to poor visual motor skills. If this is the case with your child, perhaps he could complete the timed tests orally, thus removing the primary barrier.
Just a vent - my daughter was forced to drop from honors math in HS because everything was timed. Her freshman year, she NEVER completed a test. It doesn't take a mathematician to figure out if you don't finish, your average goes down quickly. We had her tested that summer and found she has a low PSI index relative to her VCI and PRI as well as some other quirky issues. We were able to secure a 504 plan that gave her accommodations (extra time), and it is amazing what happened to her grades in all subjects. Her anxiety was reduced and she was able to complete and check her work. Unfortunately, she had already dropped to college prep math and was unable to get back on track to honors by the time the 504 was granted..
