This study seems to ignore the most obvious differences between standardized tests and typical classroom grades. Standardized tests tend to capture a single type of work (getting the right answer, regardless of process) in a single moment (test day) with an objective evaluation (multiple choice). Whereas classroom grades take into account various sorts of work, including process work, over time, and inevitably take into account a variety of skills and performance beyond the “right answer on test day”.

Which is “better”? Impossible to say. Neither captures the whole picture. But the headline and apparent conclusion of the study is misleading at best.