My 8 year old also has a big gap with PSI being the lowest (in her case 94, I think). In her case, it's a problem because it is also reflected in her work in class. She is very slow with written work in class. The psych said that it is likely her ADHD but seemed mystified because her working memory index was in the 96th percentile. So obviously she is able to hold info in her mind and manipulate multiple pieces of info, which is something that usually those with ADHD have trouble with. Usually with ADHD, both processing speed and working memory are lower. So why high working memory and low processing speed in my DD's case? A different learning disability? He is going to do more testing to try to figure it out.
DD has a similar GAI (a little higher and her verbal and PRI scores are reversed from yours, with PRI being higher), and she did do a grade skip, in her case she went from second quarter of kindergarten to second quarter of first grade. It wasn't a problem and she's doing well in the next grade up, but a grade skip easier to do when kids are younger than older. You will want to look at achievement testing and what she knows, and make sure she wouldn't miss anything major by skipping a grade.
