Data such as standardized test scores can only tell us so much. For one thing, children are not standardized.
Which group of teachers should benefit more? The ones that forcefully receive resources from the taxpayers, or the ones that produce educational outcomes that are desired by children and parents?
Like any other economic good, the value of a higher education degree is determined on the market, at the intersection of the subjective valuations and appraisements of those constituting the supply and demand of that particular good.