Yes, I got 50% extra time on both the SAT and the ACT as well as being able to test in a room that had a significantly less amount of people in it. My advice is to have your psychologist help you with submitting the necessary forms to the college board. They are not going to just want scores of an academic test to prove that you need extra time. You aren't proving that extra time helps you (unless you can submit an IEP or a 504 plan that shows that you received extra time). You are proving that your ability to take a test like the SAT is hindered when you don't have the extra time. Does that make sense? They are going to want the test scores of the tests that your psychologist used to diagnose you (if he/she used any). An official diagnosis goes a long way- if you have the means to get yourself evaluated by someone who specializes in diagnosing learning disabilities and ADHD, then I would do that. I had mine done by a neuropsychologist. I went through 7 hours of testing and received a 16 page report explaining the tests he administered and my results. A full work up can be good evidence for the college board. If you don't have the time/ability to get a full evaluation, I would definitely have your psychologist write up a letter of suggestion with his recommendations for your treatment and any accommodations that he sees necessary and beneficial (that would be where he mentions the extra time). Lastly, if you have a learning specialist or a college counselor at your school, I would get them involved as well. If they can verify that you have indeed received extra time in the academic setting, that is good evidence as well. They can also assist you in completing the forms that the college board is sending you to fill out and helping you gather all of your evidence into one packet.

Hope this helps!