Read this and answer the question. If the question is unanswerable, say "unanswerable".

According to a study done by Helmut Fend (who had always been a fierce proponent of comprehensive schools) revealed that comprehensive schools do not help working class students. He compared alumni of the tripartite system to alumni of comprehensive schools. While working class alumni of comprehensive schools were awarded better school diplomas at age 35, they held similar occupational positions as working class alumni of the tripartite system and were as unlikely to graduate from college.

Who never conducted a study on comprehensive schools?
unanswerable