FWIW, our school says they can't excuse the higher level kids from all the review because the kids sometimes score poorly since the test isn't aligned to what they are learning this year, but more to what they learned a year or more ago.
I think this is why the district now refuses to subject accelerate (or even differentiate in the classroom with anything more than "enrichment" of concepts being learned). They are worried the accelerated kids will forget the concepts that are on the test for their grade level, or that there will be "gaps" and they show up on the test.
We used this against our school and as a
valid (Ha!) argument for an official acceleration. After all, we reasoned, it would be a terrible shame if DD were to
not do well simply because she was overthinking questions that she would have found on-level (ha! again) two or three years in the past....
yes, indeed... what a shame that would be... what to do... what to do...
Oh, hey-- I have an idea-- we could make it so that DD is taking the test that aligns with what she is seeing in class this year! 
{Yes, sorry to say, this worked.}
Test prep. Oh my. DD was
required to complete at least an hour of pure test prep (Study Island)
every week until she had passed state testing each year from 4th through 8th grade. She was
elated when that disappeared in high school-- she referred to Study Island as "The Rock" if that tells you anything. It
seriously angered her that she couldn't just pre-test, post-test, and bag the rest. She had to run through
all of the topic tests, which were nothing more than an annoyance to her.
She also usually 'failed' this "class" because her
participation was inadequate. That's right. She was earning 95% + on the
post-tests for the school year in SEPTEMBER, but got F grades because she wasn't spending enough
time on it each week.
Words simply cannot express how stupid this is.
I will say that our school at least didn't tie the curriculum to testing the way that I know others do, however. It was sequestered in that one "class" that wasn't really a class. Oh, sure, it was labeled something innocent like "study skills" or "academic success" or some such thing.