I've written several times recently about how short term gains in test scores are not associated with improved later life outcomes for students. (jaypgreene.com)
Students in public schools faced with increased private school competition showed greater gains in test scores than students in other public schools with the introduction of the program. (caldercenter.org)
It's true that there is more random error in measuring gains in test scores than in measuring the level of test scores. (educationnext.org)