Tammy-
I just checked the YS site and it looks like they are very specific about which tests they will accept. So I'd suggest that you specifically ask the school if they will administer the KTEA, WIAT, or W-J achievement. Unless your contact at DITD said that any achievement test will be fine, you need to be sure to get the "right" test. These are all common enough, but the school may not be cool with your wanting the numbers for admission to DITD. I'd recommend that you put your request in writing and be specific about why you feel you need the information. If you say, "I want to better understand his various levels of functioning as he seems to be somewhat asynchronous" or (this is a hot button!) "I suspect a learning disability" you will probably be fine. As I understand it, if a disability is suspected and you make a request in writing, the school has X number of days to take action.
good luck!