Michel, Sorry, but this is bullsheet. You need to get the phone added to his 504 plan. We have our’s on our son’s and they can’t legally separate him from his phone, even for the SAT or ACT. (although for the big tests you have to do an additional step and get registered with the testing company).
The one teacher that tried this year ran into the principle and an angry daddy bear, and that ended that.
If my bear cub ever got caught cheating with his phone, the school would be the least of his worries.