BTW, it is not too late for a 504 or IEP to be useful, if any further education is potentially in the offing. If the team develops a slate of accommodations that are actually helpful, these can become the foundation of accommodations in post-secondary education (though not all unis will agree to all accommodations). Each year, I write a handful of upperclassmen onto IEPs or 504s mainly for that reason.
At this point early Dec of junior year it could take till second semester is almost half over to get a 504. Almost always takes longer than you think it will. Therefore I would focus on getting the school to make reasonable accommodations now with out it because as a junior in H.S. there isn't a lot of wiggle room. You can also pursue testing and I do recommend it as it can be helpful for college.
My experience with my DD (had an IEP for LD's) is it's not the IEP/504 that the university cares about but the testing. What I found was that this testing/504's/IEP's aren't important in the college admissions process. The only place in most college apps is the a short answer response to a question about "extenuating circumstances" that the student can often optionally write. But once student has been accepted and many school will talk with your child about the testing results in their disabled students but insist on make their own evaluations of what services are needed.
