Yes, it does happen. I've especially heard of it in relationship to kids who are on the spectrum (diagnosed or not) or who had spectrum traits. As another poster said I don't necessarily think the video games are causing it though there can be an addictive component. More often, it is the case that the video games end up being the place an unhappy kid who isn't adjusting well buries himself. Or, even a lesser level kids who aren't good at coping with anxiety, stress, concentration can flit back and forth from online to schoolwork which is not a habit that works well over the long term.
I do think it is a reasonable concern and a good reminder that with a middle schooler it is important that they start to learn to tune out distractions and take personal responsibility for their work. I prefer "work before play" rather than interspersing studying with video games, you tube or Facebook. The interspersing approach might seem like a functional one during k-12 but the increasing demands of APs or college may start to make it clear why that doesn't work very well.
