Additional research with a more diverse sample is needed to verify the replicability and validity of conclusions drawn here. (scirp.org)
In contrast, value - added scores are typically computed for teachers who work in different schools — comparisons that pose special challenges to the validity of conclusions drawn. (carnegieknowledgenetwork.org)
But a review of Horn's data reveals a number of problems, raising serious questions about the validity of his conclusions and justification for his recommendations. (voxfelina.com)