`  ==Efforts to edit out POV from research section==  The former ``Research results`` section contained only supportive research. Criticism of this section came before this in the Criticism section, which gave the casual reader the impression that these were solid results that had not been challenged.  I retitled the research as ``Supportive research`` and left the criticism in a separate section, but placed it after the supportive material and subdivided it so that the section headings show that the research has been challenged.  I have edited the ``Supportive research`` so that it is clear that the results are not without challenge.  In the subsection ``Criticism of supportive achievement studies`` I have emphasized that self-selection of students for testing is a major issue in potentially biasing the test results.  `