At highschool, I played video games to death on the weekends and during the term breaks because that was the only time I was allowed to do so. Towards the end, when school became more important, I probably played video games even more.
I can remember in my final year of high school, during the exam period, I got out the original Xbox (it was november 2007). Didn't effect my grades in the least. I ended up doing fine, well, in fact, much much better than fine if I can say that without sounding like an immodest prick.
Teachers around the world will hate me for this, but I don't think homework (particularly the typical, useless homework) isn't as important as simply paying attention in class, this dependant on the quality of the teacher of course.