No, this study, it's probably correct. I have no reason to assume lack of significance or a flawed, correlational design. However, the study discusses CORRELATION not CAUSATION. I'm fine with the study, i'm just not fine with the people on both sides, for and against, video games who want this study to imply causation when it doesn't. Some people want it to be another ignorant attack against games, others want it to be scientific evidence discrediting games. Meanwhile, the people doing this study are just showing their data in a fairly impartial way whilst everyone else tries to twist it to their side.
I'm very sympathetic towards real research Psychologists. Half their field is done by people making up bullshit, the other half is studies that people with no grounding in science discredit by trying to put words in their mouths. Look, when science gets right down to it, Games are going to be no more harmful then any other media. Because I know that, I am not afraid of any study, no matter what it is setting out to discover. The likely fact that extensive gaming can indicate less likelihood of continuing your education is the first step towards finding a more salient cause for the decreased ambition.