I have read more like Elizabeth states... that it is not a straight IQ test (and therefore, it wouldn't be an even swap for the WISC IV) but no personal experience. I wouldn't find it surprising if at grade 7 some achievement piece would be involved to gain entry into a program.
What I do have experience with is needing to re-qualify for our 'enrichment program' at the end of year 2, 4 and 6 (not sure beyond, our school is preschool - year 12). Given it is matrix reasoning plus achievement across multiple subjects (so a math star who is average in other ways wouldn't make the cut)... kids do become unqualified and vice versa. Doesn't say a lot for the quality of the program or criteria!
Best of luck to you and your son on getting this sorted :-)
