The only way that it could be an accurate statement that test prep is causing worse outcomes would be if there was a negative coefficient on test prep in a head - to - head competition in a regression model — though even then, one would have to worry about endogeneity: maybe teachers with worse - performing students focus more on test prep, or maybe lower - performing students perceive test prep to be more oppressive (of course, this could go the other way as well.) (jaypgreene.com)
On this view, cultural cognition can be seen as injecting a biasing form of endogeneity into a process roughly akin to Bayesian updating. (culturalcognition.net)
Cognitive Ability, Heterogeneity, Endogeneity and Returns to Schooling in Chile: Outcomes of the 1981 Capitation Grant Scheme (semanticscholar.org)