This research study is filled with "hyperbolic statements" and rife with methodological problems. Important insights can be gleaned but teachers should read with a skeptical eye. As Harvard scholar Heather Hill notes in her critique, the report has "compelling information" but makes claims such as more effective teachers should have larger class sizes, or that charter school practitioners are more effective than their district counterparts are not grounded in the evidence they offer. The researchers ignore the many problems with broad claims about teacher effectiveness and PD using value-added data -- especially given the "unreliability and potential inaccuracy of the evaluation data." Professional development is ineffective, because of its one-size fits all formats and limited time for teachers to learn from each other.