Sorry to be the bearer of bad news, but it will be ten times as hard in college, where there is no child find mandate, and they can make you go to each professor, every single term, to advocate for accommodations. Oh, and require fresh documentation every year (at a couple of thousand bucks--or more--a pop).
As an education professional, these kinds of stories really make me angry with, and embarrassed for, my professional colleagues.
One tactic to try with the "but it's standard procedure for everyone" line is to point out that not all schools are as "good" as this one, and you want to be prepared, in the event that some unexpected life circumstance forces you to move elsewhere, with a 504 document that would help the new setting provide your child with all his necessary accommodations. Also, at some point, you will have to consider the paper trail for college, as college 504s usually take as their starting point the last few high school 504s.
