Test scores have fallen dramatically since caleb mitchell became senior class president; therefore, mitchell has done a terrible job as president. which logical fallacy does the example contain?

The answer is "false causality".

The fallacy of false causality, also known as "false cause" or called by the Latin expression, "post hoc, which means after this, in this manner along these lines. A paradox of false reason shows that since one occasion took after another in time, the main more likely than not caused the second. While a causal relationship may really exist, the announcement does not give enough data to represent truth behind the association. Such proclamations jump to a determination inferring a causal relationship without supporting proof.