One of Hoxby's most-cited papers, "Does Competition among Public Schools Benefit Students and Taxpayers?" (American Economic Review, 2000), argues that increased school choice improves educational outcomes for all students. Her methods in the paper have attracted serious criticism: Jesse Rothstein (at the time, a graduate student at UC Berkeley under Professor David Card
) published a paper claiming that he was unable to replicate her results.
Hoxby published a response in defense of her original work a few months later.
Stanford Professor Sean F. Reardon also published a critique of her evaluation of the effectiveness of New York City's charter schools claiming that her report “relie[d] on an inappropriate set of statistical models to analyze the data…[that] appear to overstate the cumulative effect of attending a charter school. In addition, the report does not provide enough technical discussion and detailed description to enable a reader to assess the validity of some aspects of the report’s methodology and results.” 
Caroline Hoxby - Wikipedia, the free encyclopedia