Well, it should be useful in advocating ...
... but my ds's school wasn't inclined to use his MAP scores to differentiate. Maybe your dc's school will be more open to the idea. I was aghast at how my ds-then-5's teacher and administrators had his info sitting in front of them (RIT 186 in January, 192 in April as a Ker, not to mention his 3SD+ IQ score AND his >99.9 percentile WIAT achievement scores), and still refused to do anything about it.
Don't mean to sound all gloom-and-doom -- I hope your school is more receptive than my ds's was. Just know that what seems pretty cut-and-dry to you may not take shape as you hope, so be prepared for a -- I don't want to say "battle," but at least a push back from the school. I thought my ds's scores screamed for some differentiation at the very least, and preferably acceleration since his reading scores were almost equally high, but it didn't end up that way -- "social concerns," "organizational concerns" and all.
Can you tell we had a pretty bad experience and I'm just a *snitch* disillusioned?
