UGH, it's all so confusing. I've been trying to sort this out for awhile now. I remember his teacher saying that the SRI scores topped out at 1100? (I don't recall the exact #) which was about 11th grade. She did say that DSs was off the charts which would indicate 11+. However, on the Lexile Map, 1100 is 9th gr level, which doesn't quite correspond with the 7.3 on the link you provided. Also, on the 'score' sheet they send home, it shows the average/quarter for 3rd grade in the 500s, which does correspond with the Lexile Map.
I guess it doesn't really matter, it's just frustrating to have conflicting info on something that (I feel) should be pretty simple and black/white, kwim? I think I give up, LOL.
Anyway, thanks for the info.