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.)
On this view, cultural cognition can be seen as injecting a biasing form of
endogeneity into a process roughly akin to Bayesian updating.
Cognitive Ability, Heterogeneity,
Endogeneity and Returns to Schooling in Chile: Outcomes of the 1981 Capitation Grant Scheme
And they also noted that any causal claim about the relative effectiveness of test prep would require some effort to address
the endogeneity of which teachers engage in more test prep.
By exploiting exogenous variation in career concerns in the form of principal turnover, the author shows the observed behaviors can not be due to
the endogeneity of teacher mobility decisions alone.
Using longitudinal data, we investigate how student outcomes change in relation to this initiative with an instrumental variables strategy that counters
the endogeneity of student assignment across schools before and after the restructuring occurred.