OK, I'm going to answer first without reading the replies, then I'll go back and read them
So fwiw, I would NOT allow them to do this at all. Both for the reasons you've written above (math should be about math, not handwriting OT - for all the reasons you listed), and (jmo) I think they may be a bit misguided in their OT effort. I absolutely think OT is a good thing to do - our dysgraphic ds went through around 9 months of OT after he was diagnosed at 8, and it helped him develop legible handwriting, and workable pencil grip, posture etc and eliminated wrist pain. All that was *very* worthwhile. What it didn't do was "cure" his dysgraphia. He still accidentally switches numbers around and makes a ton of copying mistakes when he is working through math problems by hand, and he still has to semi-consciously think about how to form each number/letter when he writes. IMO, if the school wants to help your ds with *math* accommodations, then they should be helping him learn how to type out his math on his iPad. If they want to offer OT for him to learn proper posture, letter formation etc, that's great - but do it as a pull-out that is focused only on the handwriting remediation, and when he's in class, have him using his accommodations.
OK, so I can get a bit passionate about that lol! FWiW, my opinions on the subject were strongly shaped first by my ds' neuropsych, who recommended when he was first diagnosed that we do what we can to help ds learn how to write his letters and have him go through OT to remediate posture, grip, etc... and then let it go and focus on AT. More than 6 years down the road, I realize how right (at least for our ds) that advice was.
Now I'm going back to read the replies
polarbear
