Yes, as PP said, it's more typically seen on a 504 as a stand alone (though also as PP said some schools won't do) and wouldn't be stand alone on an IEP. That said, 5 is still within the developmental delay category age range, where one potential area of delay is motor skills, and a delay here could actually very well be impacting him - in writing, adaptive tasks (self care, dressing, other things like that, sort of functioning skills), etc - he's still young enough they should be looking at a much broader definition of "academics" than you might typically think of.
Anyway, either way, at 5 they're going to route you to Early Stages, for an evaluation (Early Stages does evals for ages 3-5, regardless of whether a kid is enrolled at a school). Early Stages will do a fuller eval - cognitive, educational, OT, (more if you have more concerns in other areas), which lets them see if there are any delays, if there's an impact on participation/academics. So you might as well just call early stages yourself, now, to get the ball rolling. I suppose it's theoretically possible that there's some way to try to get it via a 504 dealing only with the school, but usually they put you through the whole special ed eval process even for that, and frankly you want an IEP if you can get one, over a 504 plan.
I'd call now - it's a long timeline (120 days), you want to start it now. And then follow up on your call with a request in writing, as often they insist only a written request starts the timeline. Or do the request in writing initially (via the link below, I'd do by email so you have a record). But somewhere in there make sure they interface with your kid's teacher, after he starts school, so they have a good picture of whether any of this is impacting him in the classroom.
http://www.earlystagesdc.org/for-families/make-an-appointment